Base station radio resource management

ABSTRACT

A first base station may transmit a first physical downlink channel associated with one or more wireless devices in communication with the first base station, wherein the first physical downlink control channel is transmitted in fewer than all subframes of a frame and begins in time at a first symbol number in a series of symbols of a subframe. A second base station may transmit a second physical downlink control channel associated with one or more wireless devices in communication with the second base station. Second radio resources of the second physical downlink control channel may be configured based on the first symbol number of the first physical downlink control channel to manage overlap with first radio resources of the first physical downlink control channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/615,347, filed Mar. 25, 2012, entitled “Control Channel InformationExchange between Base Stations,” and U.S. Provisional Application No.61/642,472, filed May 4, 2012, entitled “Reference Signals and ChannelFeedback in Wireless Networks,” which are hereby incorporated byreference in their entirety.

SUMMARY

The present disclosure involves, among other features, configuration ofradio resources of physical downlink control channels used by basestations. For example, a second base station may configure radioresources, of a second physical downlink control channel, based on afirst symbol number of a first physical downlink control channel of afirst base station. The first base station may indicate, to the secondbase station, the radio resources of the first physical downlink controlchannel. Of course, this Summary is not an exhaustive summary of theentire disclosure, and should not be deemed a limitation on the scope ofthis patent.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

An example embodiment of the present invention is described herein withreference to the drawings, in which:

FIG. 1 is a diagram depicting example sets of OFDM subcarriers accordingto an example embodiment;

FIG. 2 is a diagram depicting an example transmission and reception timefor two carriers, according to an example embodiment;

FIG. 3 is a diagram depicting OFDM radio resources according to anexample embodiment;

FIG. 4 is a block diagram of a base station and a wireless device,according to an example embodiment;

FIG. 5 is a diagram depicting time and frequency resources for twocarriers according to an example embodiment;

FIG. 6 is a diagram illustrating transmission of data and controlinformation according to an example embodiment;

FIG. 7 is a diagram illustrating uplink and downlink subframes accordingto an example embodiment; and

FIG. 8 is a block diagram illustrating an encryption mechanism accordingto an example embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention provide methods and systems forcontrol channel information transmission between base stations. Thetechnology disclosed herein is in the technical field of multicarriercommunication systems. More particularly, the technology disclosedherein is related to a method and system for control channel informationtransmission between base stations in a multicarrier communicationsystem.

Example embodiments of the invention may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA (codedivision multiple access), OFDM (orthogonal frequency divisionmultiplexing), TDMA (time division multiple access), Wavelettechnologies, and/or the like. Hybrid transmission mechanisms such asTDMA/CDMA, and OFDM/CDMA may also be employed. Various modulationschemes may be applied for signal transmission in the physical layer.Examples of modulation schemes include, but are not limited to: phase,amplitude, code, a combination of these, and/or the like. An exampleradio transmission method may implement QAM (quadrature amplitudemodulation) using BPSK (binary phase shift keying), QPSK (quadraturephase shift keying), 16-QAM, 64-QAM, 256-QAM, and/or the like. Physicalradio transmission may be enhanced by dynamically or semi-dynamicallychanging the modulation and coding scheme depending on transmissionrequirements and radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention. As illustrated in thisexample, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, SC-OFDM (single carrier-OFDM) technology, or the like.For example, arrow 101 shows a subcarrier transmitting informationsymbols. FIG. 1 is for illustration purposes, and a typical multicarrierOFDM system may include more subcarriers in a carrier. For example, thenumber of subcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD (frequency divisionduplex) and TDD (time division duplex) duplex mechanisms. FIG. 2 showsan example FDD frame timing. Downlink and uplink transmissions may beorganized into radio frames 201. In this example, radio frame durationis 10 msec. Other frame durations, for example, in the range of 1 to 100msec may also be supported. In this example, each 10 ms radio frame 201may be divided into ten equally sized subframes 202. Other subframedurations such as including 0.5 msec, 1 msec, 2 msec, and 5 msec mayalso be supported. Sub-frame(s) may consist of two or more slots 206.For the example of FDD, 10 subframes may be available for downlinktransmission and 10 subframes may be available for uplink transmissionsin each 10 ms interval. Uplink and downlink transmissions may beseparated in the frequency domain. Slot(s) may include a plurality ofOFDM symbols 203. The number of OFDM symbols 203 in a slot 206 maydepend on the cyclic prefix length and subcarrier spacing.

In an example case of TDD, uplink and downlink transmissions may beseparated in the time domain. According to some of the various aspectsof embodiments, each 10 ms radio frame may include two half-frames of 5ms each. Half-frame(s) may include eight slots of length 0.5 ms andthree special fields: DwPTS (Downlink Pilot Time Slot), GP (GuardPeriod) and UpPTS (Uplink Pilot Time Slot). The length of DwPTS andUpPTS may be configurable subject to the total length of DwPTS, GP andUpPTS being equal to 1 ms. Both 5 ms and 10 ms switch-point periodicitymay be supported. In an example, subframe 1 in all configurations andsubframe 6 in configurations with 5 ms switch-point periodicity mayinclude DwPTS, GP and UpPTS. Subframe 6 in configurations with 10 msswitch-point periodicity may include DwPTS. Other subframes may includetwo equally sized slots. For this TDD example, GP may be employed fordownlink to uplink transition. Other subframes/fields may be assignedfor either downlink or uplink transmission. Other frame structures inaddition to the above two frame structures may also be supported, forexample in one example embodiment the frame duration may be selecteddynamically based on the packet sizes.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or resource blocks (RB) (in this example 6 to 100RBs) may depend, at least in part, on the downlink transmissionbandwidth 306 configured in the cell. The smallest radio resource unitmay be called a resource element (e.g. 301). Resource elements may begrouped into resource blocks (e.g. 302). Resource blocks may be groupedinto larger radio resources called Resource Block Groups (RBG) (e.g.303). The transmitted signal in slot 206 may be described by one orseveral resource grids of a plurality of subcarriers and a plurality ofOFDM symbols. Resource blocks may be used to describe the mapping ofcertain physical channels to resource elements. Other pre-definedgroupings of physical resource elements may be implemented in the systemdepending on the radio technology. For example, 24 subcarriers may begrouped as a radio block for a duration of 5 msec.

Physical and virtual resource blocks may be defined. A physical resourceblock may be defined as N consecutive OFDM symbols in the time domainand M consecutive subcarriers in the frequency domain, wherein M and Nare integers. A physical resource block may include M×N resourceelements. In an illustrative example, a resource block may correspond toone slot in the time domain and 180 kHz in the frequency domain (for 15KHz subcarrier bandwidth and 12 subcarriers). A virtual resource blockmay be of the same size as a physical resource block. Various types ofvirtual resource blocks may be defined (e.g. virtual resource blocks oflocalized type and virtual resource blocks of distributed type). Forvarious types of virtual resource blocks, a pair of virtual resourceblocks over two slots in a subframe may be assigned together by a singlevirtual resource block number. Virtual resource blocks of localized typemay be mapped directly to physical resource blocks such that sequentialvirtual resource block k corresponds to physical resource block k.Alternatively, virtual resource blocks of distributed type may be mappedto physical resource blocks according to a predefined table or apredefined formula. Various configurations for radio resources may besupported under an OFDM framework, for example, a resource block may bedefined as including the subcarriers in the entire band for an allocatedtime duration.

According to some of the various aspects of embodiments, an antenna portmay be defined such that the channel over which a symbol on the antennaport is conveyed may be inferred from the channel over which anothersymbol on the same antenna port is conveyed. In some embodiments, theremay be one resource grid per antenna port. The set of antenna port(s)supported may depend on the reference signal configuration in the cell.Cell-specific reference signals may support a configuration of one, two,or four antenna port(s) and may be transmitted on antenna port(s) {0},{0, 1}, and {0, 1, 2, 3}, respectively. Multicast-broadcast referencesignals may be transmitted on antenna port 4. Wireless device-specificreference signals may be transmitted on antenna port(s) 5, 7, 8, or oneor several of ports {7, 8, 9, 10, 11, 12, 13, 14}. Positioning referencesignals may be transmitted on antenna port 6. Channel state information(CSI) reference signals may support a configuration of one, two, four oreight antenna port(s) and may be transmitted on antenna port(s) 15, {15,16}, {15, . . . , 18} and {15, . . . , 22}, respectively. Variousconfigurations for antenna configuration may be supported depending onthe number of antennas and the capability of the wireless devices andwireless base stations.

According to some embodiments, a radio resource framework using OFDMtechnology may be employed. Alternative embodiments may be implementedemploying other radio technologies. Example transmission mechanismsinclude, but are not limited to: CDMA, OFDM, TDMA, Wavelet technologies,and/or the like. Hybrid transmission mechanisms such as TDMA/CDMA, andOFDM/CDMA may also be employed.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present invention.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to some of the various aspects of embodiments, transceiver(s)may be employed. A transceiver is a device that includes both atransmitter and receiver. Transceivers may be employed in devices suchas wireless devices, base stations, relay nodes, and/or the like.Example embodiments for radio technology implemented in communicationinterface 402, 407 and wireless link 411 are illustrated are FIG. 1,FIG. 2, and FIG. 3. and associated text.

An interface may be a hardware interface, a firmware interface, asoftware interface, and/or a combination thereof. The hardware interfacemay include connectors, wires, electronic devices such as drivers,amplifiers, and/or the like. A software interface may include codestored in a memory device to implement protocol(s), protocol layers,communication drivers, device drivers, combinations thereof, and/or thelike. A firmware interface may include a combination of embeddedhardware and code stored in and/or in communication with a memory deviceto implement connections, electronic device operations, protocol(s),protocol layers, communication drivers, device drivers, hardwareoperations, combinations thereof, and/or the like.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayalso refer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics inthe device, whether the device is in an operational or non-operationalstate.

FIG. 5 is a block diagram depicting a system 500 for transmitting datatraffic generated by a wireless device 502 to a server 508 over amulticarrier OFDM radio according to one aspect of the illustrativeembodiments. The system 500 may include a Wireless CellularNetwork/Internet Network 507, which may function to provide connectivitybetween one or more wireless devices 502 (e.g., a cell phone, PDA(personal digital assistant), other wirelessly-equipped device, and/orthe like), one or more servers 508 (e.g. multimedia server, applicationservers, email servers, or database servers) and/or the like.

It should be understood, however, that this and other arrangementsdescribed herein are set forth for purposes of example only. As such,those skilled in the art will appreciate that other arrangements andother elements (e.g., machines, interfaces, functions, orders offunctions, etc.) may be used instead, some elements may be added, andsome elements may be omitted altogether. Further, as in mosttelecommunications applications, those skilled in the art willappreciate that many of the elements described herein are functionalentities that may be implemented as discrete or distributed componentsor in conjunction with other components, and in any suitable combinationand location. Still further, various functions described herein as beingperformed by one or more entities may be carried out by hardware,firmware and/or software logic in combination with hardware. Forinstance, various functions may be carried out by a processor executinga set of machine language instructions stored in memory.

As shown, the access network may include a plurality of base stations503 . . . 504. Base station 503 . . . 504 of the access network mayfunction to transmit and receive RF (radio frequency) radiation 505 . .. 506 at one or more carrier frequencies, and the RF radiation mayprovide one or more air interfaces over which the wireless device 502may communicate with the base stations 503 . . . 504. The user 501 mayuse the wireless device (or UE: user equipment) to receive data traffic,such as one or more multimedia files, data files, pictures, video files,or voice mails, etc. The wireless device 502 may include applicationssuch as web email, email applications, upload and ftp applications, MMS(multimedia messaging system) applications, or file sharingapplications. In another example embodiment, the wireless device 502 mayautomatically send traffic to a server 508 without direct involvement ofa user. For example, consider a wireless camera with automatic uploadfeature, or a video camera uploading videos to the remote server 508, ora personal computer equipped with an application transmitting traffic toa remote server.

One or more base stations 503 . . . 504 may define a correspondingwireless coverage area. The RF radiation 505 . . . 506 of the basestations 503 . . . 504 may carry communications between the WirelessCellular Network/Internet Network 507 and access device 502 according toany of a variety of protocols. For example, RF radiation 505 . . . 506may carry communications according to WiMAX (Worldwide Interoperabilityfor Microwave Access e.g., IEEE 802.16), LTE (long term evolution),microwave, satellite, MMDS (Multichannel Multipoint DistributionService), Wi-Fi (e.g., IEEE 802.11), Bluetooth, infrared, and otherprotocols now known or later developed. The communication between thewireless device 502 and the server 508 may be enabled by any networkingand transport technology for example TCP/IP (transport controlprotocol/Internet protocol), RTP (real time protocol), RTCP (real timecontrol protocol), HTTP (Hypertext Transfer Protocol) or any othernetworking protocol.

According to some of the various aspects of embodiments, an LTE networkmay include many base stations, providing a user plane (PDCP: packetdata convergence protocol/RLC: radio link control/MAC: media accesscontrol/PHY: physical) and control plane (RRC: radio resource control)protocol terminations towards the wireless device. The base station(s)may be interconnected with other base station(s) by means of an X2interface. The base stations may also be connected by means of an S1interface to an EPC (Evolved Packet Core). For example, the basestations may be interconnected to the MME (Mobility Management Entity)by means of the S1-MME interface and to the Serving Gateway (S-GW) bymeans of the S1-U interface. The S1 interface may support a many-to-manyrelation between MMEs/Serving Gateways and base stations. A base stationmay include many sectors for example: 1, 2, 3, 4, or 6 sectors. A basestation may include many cells, for example, ranging from 1 to 50 cellsor more. A cell may be categorized, for example, as a primary cell orsecondary cell. When carrier aggregation is configured, a wirelessdevice may have one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell may providethe NAS (non-access stratum) mobility information (e.g. TAI-trackingarea identifier), and at RRC connection re-establishment/handover, oneserving cell may provide the security input. This cell may be referredto as the Primary Cell (PCell). In the downlink, the carriercorresponding to the PCell may be the Downlink Primary Component Carrier(DL PCC), while in the uplink, it may be the Uplink Primary ComponentCarrier (UL PCC). Depending on wireless device capabilities, SecondaryCells (SCells) may be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellmay be a Downlink Secondary Component Carrier (DL SCC), while in theuplink, it may be an Uplink Secondary Component Carrier (UL SCC). AnSCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,is assigned a physical cell ID and a cell index. A carrier (downlink oruplink) belongs to only one cell, the cell ID or Cell index may alsoidentify the downlink carrier or uplink carrier of the cell (dependingon the context it is used). In the specification, cell ID may be equallyreferred to a carrier ID, and cell index may be referred to carrierindex. In implementation, the physical cell ID or cell index may beassigned to a cell. Cell ID may be determined using the synchronizationsignal transmitted on a downlink carrier. Cell index may be determinedusing RRC messages. For example, when the specification refers to afirst physical cell ID for a first downlink carrier, it may mean thefirst physical cell ID is for a cell comprising the first downlinkcarrier. The same concept may apply to, for example, carrier activation.When the specification indicates that a first carrier is activated, itequally means that the cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in wireless device, base station, radio environment, network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, theexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

According to some of the various aspects of embodiments, a base stationmay receive a first radio resource control (RRC) message from a wirelessdevice (UE). The first message may be received on a primary carrier(uplink) during the connection set up process. The first message may bea UE capability information message. The UE may transfer its radioaccess capability information to the eNB (E-UTRAN). If the UE haschanged its E-UTRAN radio access capabilities, the UE may request higherlayers to initiate a procedure that would result in the update of UEradio access capabilities using a new RRC connection. A UE may be ableto communicate with the E-UTRAN about its radio access capabilities,such as the system (including the release and frequency band) that theUE supports, the UE receive and transmit capabilities (single/dualradio, dual receiver), and/or the like. The first RRC message maycomprise one or more parameters indicating whether the wireless devicesupports an enhanced physical downlink control channel (ePDCCH). Thefirst RRC message may comprise one or more parameters providinginformation (explicitly or implicitly) on whether the wireless devicesupports new carrier types (NCT). Example of NCTs are stand alone NCT,synchronized NCT, unsynchronized NCT, and/or the like.

The base station may transmit selectively and if the one or moreparameters indicates support of ePDCCH, at least one second RRC messageconfigured to cause, in the wireless device, configuration of one ormore ePDCCHs. The base station may receive UE capability informationfrom the wireless device. If the wireless device does not supportePDCCH, then the base station does not configure ePDCCH for the wirelessdevice. If the wireless device indicates that it supports ePDCCHconfiguration, the base station may decide to configure ePDCCH or not toconfigure ePDCCH for the wireless device. This decision is based oninternal base station mechanisms, and may be based, at least in part, onbase station configuration settings, UE QoS profile, UE bearers,mobility, a combination thereof, and/or the like.

The at least one second RRC message configured to cause, in the wirelessdevice, configuration of ePDCCH on existing configured carriers (forexample a primary cell, a secondary cell), or on newly added cells(legacy or NCT cell). The at least one second RRC message may furthercause, in the wireless device, configuration of other radio channels andparameters, such as, uplink data channel, downlink data channel, uplinkcontrol channel, downlink control channel, power control parameters,measurement parameters, radio bearers, a combination thereof, and/or thelike. The at least one second RRC message configuring ePDCCH maycomprise at least one of: subframe subset configuration, ePDCCH startingposition in the subset of subframes, and at least one ePDCCHtransmission and resource configuration. Some of the parameters may beconsidered optional.

According to some of the various aspects of embodiments, an ePDCCH of adownlink carrier may be configured for a subset of subframes in aplurality of subframes. The at least one second RRC message may comprisesubframe configuration information. For example at least one second RRCmessage may comprise a bitmap indicating which subframe(s) in radioframes are configured with ePDCCH resources. The ePDCCH bitmap mayconfigure the subframes which the UE may monitor search space(s) onePDCCH. A UE may monitor a UE-specific search space in ePDCCH radioresources. The bitmap may be for example 40 bits, and may indicate theePDCCH subframes for the duration of four frames. For example, a valueof zero may indicate no ePDCCH resources in the corresponding subframefor the UE, and a value of one may indicate ePDCCH resources areconfigured for the UE in the corresponding subframe. In this example,the same pattern may be repeated in every four frame (40 subframes). Inanother example for TDD frame structure, the bitmap may be 20, 60, or 70bits. If the bitmap is not included in the at least one second messageconfiguring EPDCCH, then ePDCCH may be configured in every subframe. AUE may monitor the UE-specific search space on ePDCCH in all subframesexcept when according to some pre-defined rules when other parameters,for example, measurement parameters, may not allow monitoring of ePDCCHin that subframe.

According to some of the various aspects of embodiments, the at leastone second RRC message may comprise a starting symbol parameterindicating ePDCCH starting symbol in ePDCCH configured subframes. Thestarting symbol parameter may indicate the OFDM starting symbol for anyePDCCH and PDSCH scheduled by ePDCCH on the same cell, if the UE is notconfigured with coordinated multimode transmission mode. If startingsymbol parameter is not present in the RRC message configuring ePDCCH,the UE may derive the starting OFDM symbol of ePDCCH and PDSCH scheduledby the ePDCCH from PCFICH (format indicator parameter) transmitted inthe same subframe. In an example embodiment, values zero, one, two, andthree may applicable for dl-Bandwidth greater than ten resource blocks,and values two, three, and four may be applicable. The starting symbolparameter may not be configured employing the starting symbol parameterwhen UE is configured with coordinated multimode transmission mode.

According to some of the various aspects of embodiments, in a givensubframe of a cell, some of the UEs may be configured with ePDCCH andsome other UEs may not be configured with ePDCCH in the given subframe.The PDSCH starting position in the given subframe for UEs that areconfigured with ePDCCH in the cell may be determined employing thestarting symbol parameter. PDSCH starting position in the given subframefor UEs that are not configured with ePDCCH in the cell may bedetermined employing PCFICH or other RRC messages.

According to some of the various aspects of embodiments, the at leastone second RRC message configuring ePDCCH may comprise at least oneePDCCH transmission and resource configuration. For example, ePDCCH maycomprise one or two ePDCCH transmission and resource configuration. AnePDCCH transmission and resource configuration may be identified by anePDCCH index. The ePDCCH index may be used to add or release ePDCCHtransmission and resource configuration to or from an existingconfigured ePDCCH. The ePDCCH transmission and resource configurationmay comprise one or more parameters, including one or more of thefollowing parameters: frequency resources, frequency distribution,frequency assignment, reference sequence, corresponding uplink controlchannel parameter, and coordinated transmission mode parameters. TheePDCCH transmission and resource configuration may be applicable to thesubset of subframes in which ePDCCH is configured.

According to some of the various aspects of embodiments, frequencyresources parameter may indicate the number of physical resource-blockpairs used for the ePDCCH. For example this may have the value of two,four or six. The frequency distribution parameter may indicate whetherthe frequency resources (resource blocks) are distributed or localized.In localized distribution, resource blocks in ePDCCH transmission may becontiguous, and in a distributed distribution resource blocks in ePDCCHmay be distributed in the carrier bandwidth. The frequency assignmentparameter indicates the assignment of specific resource blocks inresource blocks of LTE carrier to the ePDCCH. The frequency assignment,for example, may be an index to a specific combination of physicalresource-block pairs for ePDCCH set as defined in a pre-defined look-uptable. The reference sequence parameter may indicate the demodulationreference signal scrambling sequence initialization parameter for ePDCCHsymbols. The corresponding uplink control channel parameter may indicatePUCCH format 1a and 1b resource starting offset for the ePDCCH set. Forexample, uplink PUCCH radio resources for transmitting ACK/NACK fordownlink transport blocks (MAC/PHY packets) transmitted in the PDSCHscheduled by ePDCCH is determined based, at least in part, employing thecorresponding uplink control channel parameter. The uplink controlchannel parameter may indicate the frequency start offset in terms ofresource blocks in the uplink carrier. The coordinated transmission modeparameters may indicate the starting OFDM symbol, the related ratematching parameters and quasi-collocation assumption for ePDCCH when theUE is configured in coordinated transmission mode. A coordinatedtransmission mode parameter may provide the index of PDSCH configurationfor coordinated transmission mode.

In another example embodiment, the same RRC message may configurecell(s) and ePDCCH in the downlink of the cell. The RRC message causingthe configuration of carriers (cells) in the wireless device maycomprise an identifier for a carrier in the plurality of carriers,information identifying a carrier type for each carrier in the pluralityof carriers, and information associating at least one non-backwardcompatible carrier (NCT) with a backward compatible carrier. The controlmessage may further comprise information associating a non-backwardcompatible carrier with a backward compatible carrier. Carrier type forexample may be backward compatible, non-backward compatible. The carriertype may further determine if the carrier is synchronized,non-synchronized, and/or a segment carrier. The carrier type maydetermine if the non-backward compatible carrier is a stand-alonecarrier or depends on (is associated with) another carrier. The carriertype information may be transmitted explicitly by a carrier typeparameter, or may be determined based one or more parameters in the RRCmessage(s).

According to some of the various aspects of embodiments, an ePDCCH maycarry scheduling assignments for uplink and downlink of one or morecells. Scheduling assignments includes transmission format (modulationand coding) and resource assignment information. The base station maytransmit first transmission format and scheduling information by thebase station on an ePDCCH in a first subframe of the subset ofsubframes. The first transmission format and the scheduling informationmay be for one or more first data packets (transport blocks) transmittedon a data channel of the first carrier. The base station may transmitthe one or more first data packets to the wireless device on the firstdata channel in the first subframe according to the transmission formatand the scheduling information.

According to some of the various aspects of embodiments, an ePDCCH of afirst carrier may provide scheduling assignment for transport blocks(packets) transmitted on uplink data channel and downlink data channelof the first carrier. Cross carrier scheduling may be configured byhigher layers (e.g., RRC), for example, for a second carrier. The ePDCCHof a first carrier may also provide scheduling assignment for transportblocks (packets) transmitted on uplink data channel and downlink datachannel of the second carrier. ACK/NACK for packets transmitted in thedownlink (according to ePDCCH assignment) may be provided in PUCCHresources identified by the corresponding uplink control channelparameter (in RRC message). ACK/NACK may also be piggybacked and betransmitted in uplink transport blocks transmitted in the uplink sharedchannel. ACK/NACK for packets transmitted in the uplink (according toePDCCH assignment) may be provided in the downlink employing physicalHARQ indicator channel of the first carrier. Radio resourceconfiguration of physical HARQ indicator channel of the first carriermay be determined according to master information block transmitted inPBCH, or may be transmitted by higher layers (e.g. RRC) when the firstcarrier is configured. HARQ radio resources (symbol(s), subcarrier(s))transmitting ACK/NACK for an uplink packet scheduled by ePDCCHassignment may be determined according to a physical resource blockoffset of the uplink resources. For example, a pre-defined relationship(e.g. look-up table, formula, relationship) may determine downlink HARQresources for an uplink packet transmitted on physical uplink sharedchannel.

According to some of the various aspects of embodiments, ePDCCHresources may be configured for one or more carriers in one or moreconfigured carriers for a wireless device. For example, ePDCCH may beconfigured for at least one of a primary carrier, a secondary carrier, abackward-compatible carrier or a non-backward compatible carrier. In anexample embodiment, the starting symbol of ePDCCH and PDSCH for aprimary carrier or for a backward-compatible secondary carrier may beone of the second, third, fourth symbol, or fifth symbol (respectivelycorresponding to symbol 1, 2, 3, 4). In another example, the startingsymbol of ePDCCH and PDSCH for a non-back-ward compatible secondarycarrier may be one of the first, second, third, fourth symbol, or fifthsymbol (respectively corresponding to symbol 0, 1, 2, 3, 4). At leastthe first symbol in a primary carrier or in a backward compatiblesecondary carrier is allocated to legacy PCFICH, legacy PDCCH and legacyHARQ channels. In a non-backward compatible secondary carrier legacyPCFICH, legacy PDCCH and/or legacy HARQ channels may be avoided as awhole in the carrier. This may increase spectral efficiency ofnon-backward compatible carriers compared with backward compatiblecarriers.

According to some of the various aspects of embodiments, an ePDCCH maybe transmitted on a backward compatible or non-backward compatiblecarrier. The ePDCCH may not be transmitted in certain subframes, e.g.,subframes configured with multicast transmission and some TDD specialsubframes. Physical multicast channel (PMCH) may occupy all resourceblocks of a carrier. RRC message(s) may cause configuration of thesubset of subframes in which a UE may monitor ePDCCH. If one theconfigured ePDCCH subframes overlaps with a PMCH subframe, the UE maymonitor UE-specific search space on PDCCH of the subframe and may notsearch ePDCCH resources on a subframe with configured PMCH transmission.In new carrier types, PDCCH may be configured for a subset of subframes.If legacy control region is configured on a new carrier type, areference signal transmitted in the control radio resource region may beused to demodulate the legacy control channel.

According to some of the various aspects of embodiments, legacy downlinkcontrol channels may be configured for subframes with configured PMCH.The subframes that are configured with PMCH may be configured withPDCCH, PCFICH, and/or PHICH. PDCCH resources in PMCH may be employed forscheduling uplink packets in an uplink subframe. This may increaseuplink spectral efficiency in a new type carrier. In another exampleembodiment, configuration parameters of PDCCH may be included in the RRCmessage configuring the new carrier type. PDCCH configuration parametersmay include at least: subframe configuration, and/or PDCCH duration.Subframe configuration parameters for example could be in the form of abitmap. For example a bitmap with length of 40 bits may indicate thesubset of subframes with configured PDCCH with a period of 4 frames. Inanother example embodiment, a subframe index and a subframe period maybe used to determine the subset of subframes with a configured PDCCH. APDCCH may occupy one, two, three or four symbols. PDCCH durationparameter in RRC message may indicate the number of symbols allocated into PDCCH. In another example embodiment, subframe configurationparameter in the RRC message may indicate the subset of subframes withconfigured PCFICH, and PDCCH configuration. PCFICH in each subframe maydetermine the duration of PCFICH in the same subframe. In anotherexample embodiment, subframe configuration parameter in the RRC messagemay indicate the subset of subframes with configured with PCFICH, PDCCH,and PHICH. PHICH radio resources may be employed for transmission ofACK/NACK in the downlink for packets transmitted in the uplink.

According to some of the various aspects of embodiments, RRC message(s)may configure cross carrier scheduling for a new type carrier. RRCmessage may configure cross carrier scheduling for a subset ofsubframes. The cross carrier scheduling configuration parameters maycomprise a bitmap indicating the subset of subframes that cross carrierscheduling is configured for a new type carrier. For example, crosscarrier scheduling may be configured for subframes including PMCHtransmission. In non-PMCH subframes, the ePDCCH of the same carrier maybe used for scheduling assignments. In PMCH subframes, the ePDCCH orPDCCH of another carrier may be employed for uplink packet assignment ofthe carrier employing cross carrier scheduling.

According to some of the various aspects of embodiments, new type (alsocalled non-backward compatible or non-prime) carriers may be configuredto work in association with another backward compatible carrier. Newcarrier types may be deployed in heterogeneous networks and/orhomogeneous networks, and may coexist with backward compatible carriersin the same base station/sector. In another example embodiment, newcarrier types may be configured on standalone bases without backwardcompatible carriers. New type carriers may have reduced legacy controlsignalling and common reference signals. The interference and overheadlevels on the new carrier types may be reduced compared to backwardcompatible carriers. A new carrier type may be synchronized with anothercarrier in the same band. In another example embodiment, a new carriertype may not be synchronized with another carrier.

New carrier types may transmit reduced or no common reference signalcompared with backward compatible carriers. In one example embodiment,new carrier type may carry one reference signal port (for example,common reference signal port 0 resource elements per physical resourceblock) and may employ legacy common reference signal sequences. Commonreference signals may be transmitted within one subframe with five msperiodicity. In this example, two of the ten subframes in a frame maytransmit common reference signals. The common reference signal may beemployed by the wireless device for example, for channel statemeasurement, time and/or frequency synchronization, receiver parameterestimation, and/or the like. Common reference signal may be transmittedon all resource blocks in the bandwidth or in a subset of resourceblock. In an example embodiment, the bandwidth of common referencesignal may be configured by higher layers (e.g. RRC layer). For example,common reference signal may be transmitted on 6 resource blocks or 25resource blocks according to RRC configuration. RRC configurationparameters for example may include at least one of: configuration ofcommon reference subframes (e.g. subframe index, periodicity, and/orbitmap configuration), frequency resources (common reference signalbandwidth, frequency offset, and/or frequency shift in resource blocks).In an example embodiment a subframe bitmap parameter may indicate thesubset of subframes transmitting common reference signals. In an exampleembodiment, a resource block bitmap parameter may indicate the resourceblocks transmitting common reference signals. Configuration of commonreference signal may consider that the reduced common reference signalmay impact the time and frequency synchronization performance and radioresource monitoring measurements. In an example embodiment, commonreference signal may be transmitted in the same subframe as the primaryand secondary synchronization signals. In another example embodiment, asubframe offset parameter may be configured by higher layers (e.g. RRC).A cell-specific frequency shift may be used for common referencesignals. The motivation of frequency shift is to reduce common referencesignal collision among neighbouring cells. In an example embodiment, thefrequency shift may be determined by the physical cell identifier. Inanother example embodiment, frequency shift may be configured employingconfiguration parameters comprised in RRC messages configuring a newtype carrier.

According to some of the various aspects of embodiments, a new typecarrier may be configured as a synchronized carrier. The UE may beconfigured to acquire time and frequency synchronization from a backwardcompatible carrier to which the synchronized carrier is associated with.In an example embodiment, RRC message(s) configuring the new typecarrier may comprise the carrier index of the backward compatiblecarrier associated with the new type carrier. The synchronized andnon-synchronized carrier may include reduced CRS transmissionconfigurable by parameters comprised in an RRC message. In an exampleembodiment, a synchronized carrier may be configured to not transmit anycommon reference signals and/or synchronization signals.

According to some of the various aspects of embodiments, primary andsecondary signals may be transmitted on a non-synchronized carrier. Theprimary and secondary synchronization signals may be transmitted in thecentre six resource blocks of a carrier. The time location of theprimary and secondary synchronization signal may be configured using RRCmessage configuring the new type carrier. In an example configuration ofa new carrier type, there may be collisions between radio resource ofprimary/secondary synchronization signals and demodulation referencesignals. To resolve this issue, demodulation reference signals may notbe transmitted when it overlaps with the synchronization signals. In anexample embodiment, primary and secondary synchronization signals maynot be transmitted on a synchronized new carrier type. This may reducesignalling overhead and increase spectral efficiency. An RRC messageconfiguring a new type carrier may provide configuration parameters forprimary and secondary synchronization signals and/or may indicatewhether primary and/or secondary synchronization signals are transmittedor not.

New carrier types may support existing and/or new transmission modescompared with backward compatible carrier. RRC layer may provideinformation to the UE indicating which transmission modes are employedfor transmission of transport blocks on a new carrier type. According tosome of the various aspects of embodiments, sounding referenceconfiguration for backward compatible carriers may be improved toinclude the capability of transmitting sounding reference signal on allactive uplink resource blocks of a carrier. In legacy sounding referencesignal configuration, sounding reference signal may not be transmittedon resource blocks of PUCCH radio resources in the uplink. Soundingreference signal configuration may be improved to include all resourceblocks employed for PUSCH (including resource blocks employed for PUCCHin legacy carrier, which are available for PUSCH in new type carriers).The SRS bandwidth may be chosen assuming that all active RBs in theuplink may be used for PUSCH. Then eNB may be able to sound any resourceblock usable for PUSCH transmission.

FIG. 5 is a diagram depicting time and frequency resources for carrierone 501 and carrier two 502 and FIG. 6 is a diagram illustratingtransmission of data and control information according to one aspect ofthe illustrative embodiments. An example embodiment of the inventionprovides a method and system for a wireless transmitter in acommunication network including a plurality of carriers. Each of theplurality of carriers may include a plurality of OFDM subcarriers.Transmission time may be divided into a plurality of subframes, and eachsubframe in the plurality of subframes may further be divided into aplurality of OFDM symbols.

The transmitter may transmit a synchronization signal including aprimary synchronization signal and a secondary synchronization signal ona first carrier 501. The synchronization signal may indicate a physicalcell ID for the first carrier 501. It may also provide timinginformation for the first carrier 501. If the second carrier is asynchronized carrier, the synchronization signal may also provide timinginformation for a second carrier 502 in the plurality of carriers.Subframe timing of the second data channel is provided by thesynchronization signal transmitted on the first carrier. Thesynchronization signal may be transmitted using a plurality ofsubcarriers in the in the middle of the frequency band of the firstcarrier 501 on the first and sixth subframes (subframe 0 and 5) of eachframe in the plurality of frames. Primary and secondary synchronizationsignal may occupy a bandwidth equal to six resource blocks. A physicalbroadcast channel (PBCH) 505 may be transmitted in slot one 504 ofsubframe 0 of the first carrier 501. According to an example embodiment,if the second carrier is a non-synchronized carrier, it may transmit itsown primary and secondary synchronization signal. In another exampleembodiment, synchronization signal may also be transmitted insynchronized carriers.

The transmitter may transmit a first plurality of data packets on afirst data channel 603 of the first carrier 606 on a first plurality ofOFDM subcarriers. A first plurality of OFDM subcarriers may exclude theplurality of subcarriers used for transmission of the primary andsecondary synchronization signals in the first and sixth subframes inthe plurality of frames.

The transmitter may transmit a first plurality of broadcast systeminformation messages on the first data channel 603. The plurality ofbroadcast system information messages include radio link configurationinformation for a wireless device receiving the first carrier 606 andthe second carrier 607 signals. The transmitter may transmit a secondplurality of data packets on a second data channel 605 on a secondplurality of OFDM subcarriers of the second carrier 607.

In one example embodiment, the second carrier may not transmitsynchronization signal, then the second plurality of OFDM subcarriers ofthe second carrier 502 may include the OFDM subcarriers in the middle ofthe frequency band of the second carrier 502 in the first and sixthsubframes in the plurality of frames. No primary synchronization signaland no secondary synchronization signal may be transmitted on the secondcarrier in radio resource. No broadcast system information message maybe transmitted on the second data channel 605. No physical broadcastchannel may be transmitted in radio resource 506. Multiple options maybe available, for example second carrier may transmit synchronizationsignal but do not transmit the physical broadcast channel. In anotherexample, both carriers may transmit both synchronization signal andphysical broadcast channel.

The first plurality of data packets and the second plurality of datapackets may be transmitted using a plurality of physical resource blocksincluding reference signal symbols and data symbols. The broadcastsystem information messages may be RRC system information blocks. Theradio link configuration information may include measurementconfiguration, uplink channel configuration or handover parameters.

The primary synchronization signal may be generated using afrequency-domain Zadoff-Chu sequence. The primary synchronization signalmay be mapped to the last OFDM symbol in slots zero and ten for FDDframe structure. The primary synchronization signal may be mapped to thethird OFDM symbol in subframes 1 and 6 for TDD frame structure.

The secondary synchronization signal may be generated using aninterleaved concatenation of two length-31 binary sequences. Theconcatenated sequence may be scrambled with a scrambling sequence givenby the primary synchronization signal. The portion of the secondarysynchronization signal transmitted in subframe zero may be differentfrom the portion of the secondary synchronization signal transmitted insubframe five.

In an example embodiment, cross carrier scheduling may be configured forthe second carrier. A control channel 602 may be transmitted on thefirst carrier 606. The control channel 602 may provide transmissionformat and scheduling information for the first plurality of datapackets and the second plurality of data packets. The control channel602 may be transmitted on the first carrier 606 starting from the firstOFDM symbol of each subframe. The control channel may be a physicaldownlink control channel. If the second carrier is a new type carrier(non-backward compatible carrier), no physical control format indicatorchannel and no physical downlink control channel may be transmitted onthe second carrier 607. Radio resources of the second data channel 605may be configured by the base station and may start from the first,second, third, fourth, or fifth OFDM symbol of a subframe of the secondcarrier 607 and end at the last OFDM symbol of each subframe of thesecond carrier 607. When cross carrier scheduling is configured, no HARQfeedback may be transmitted on the second carrier 607.

The receiver may receive a synchronization signal including a primarysynchronization signal and a secondary synchronization signal on a firstcarrier 501. The synchronization signal may indicate a physical cell IDfor the first carrier. The synchronization signal may be received usinga plurality of subcarriers in the in the middle of the frequency band ofthe first carrier 501 on the first and sixth subframes (subframe 0 and5) of each frame in the plurality of frames. A physical broadcastchannel (PBCH) 505 may be received in slot one 504 of subframe 0 of thefirst carrier 501.

The receiver may receive a first plurality of data packets on a firstdata channel 603 of the first carrier 606 on a first plurality of OFDMsubcarriers. A first plurality of OFDM subcarriers may exclude theplurality of subcarriers used for transmission of the primary andsecondary synchronization signals in the first and sixth subframes inthe plurality of frames. The receiver may receive a first plurality ofbroadcast system information messages on the first data channel 603. Theplurality of broadcast system information messages may include radiolink configuration information for the wireless receiver receiving thefirst carrier 606 and the second carrier 607 signals.

The receiver may receive a second plurality of data packets on a seconddata channel 605 on a second plurality of OFDM subcarriers of the secondcarrier 607. If synchronization signal is not transmitted on the secondcarrier or if it is transmitted on a different time, then the secondplurality of OFDM subcarriers of the second carrier 607 may include theOFDM subcarriers in the middle of the frequency band of the secondcarrier 502 in the first and sixth subframes in the plurality of frames.In a synchronized carrier that does not include primary and secondarysynchronization signal, no primary synchronization signal and nosecondary synchronization signal may be received on the second carrierin radio resource. Subframe timing of the second carrier 607 may besynchronized with subframe timing of the first carrier 606. No broadcastsystem information message may be received on the second data channel605. No physical broadcast channel may be received in radio resource506. Subframe timing of the second data channel may be provided by thesynchronization signal received on the first carrier.

The first plurality of data packets and the second plurality of datapackets are received using a plurality of physical resource blocksincluding reference signal symbols and data symbols. The broadcastsystem information messages may be RRC system information blocks. Theradio link configuration information may include measurementconfiguration, uplink channel configuration, or handover parameters.

The primary synchronization signal may be generated using afrequency-domain Zadoff-Chu sequence. The primary synchronization signalmay be mapped to the last OFDM symbol in slots zero and ten for FDDframe structure. The primary synchronization signal may be mapped to thethird OFDM symbol in subframes 1 and 6 for TDD frame structure.

The secondary synchronization signal may be generated using aninterleaved concatenation of two length-31 binary sequences. Theconcatenated sequence may be scrambled with a scrambling sequence givenby the primary synchronization signal. The portion of the secondarysynchronization signal transmitted in subframe zero may be differentfrom the portion of the secondary synchronization signal transmitted insubframe five.

A control channel 602 is received on the first carrier 606. The controlchannel 602 may provide transmission format and scheduling informationfor the first plurality of data packets and the second plurality of datapackets. The control channel 602 may be received on the first carrier606 starting from the first OFDM symbol of each subframe. The controlchannel 602 may be a physical downlink control channel. If the secondcarrier is a new type carrier, no physical control format indicatorchannel and no physical downlink control channel may be received on thesecond carrier 607. Radio resources of the second data channel 605 maystart from the first OFDM symbol of each subframe of the second carrier607 and end at the last OFDM symbol of each subframe of the secondcarrier 607. If cross carrier scheduling is configured for the secondcarrier, no HARQ feedback may be received on the second carrier 607.

FIG. 6 is a diagram illustrating data and control transmission channelsaccording to one aspect of the illustrative embodiments. An exampleembodiment of the present invention provides a method and system for awireless transmitter in a communication network including a plurality ofcarriers. Each of the plurality of carriers may include a plurality ofOFDM subcarriers. Transmission time may be divided into a plurality ofsubframes, and each subframe in the plurality of subframes may furtherbe divided into a plurality of OFDM symbols.

The transmitter may transmit a first control channel 601 on the firstOFDM symbol of each subframe 608 in the plurality of subframes of afirst carrier 606 in the plurality of carriers. Each instance of thefirst control channel 601 transmitted in a subframe 608 in the pluralityof subframes may indicate the number of OFDM symbols in the subframethat are preferably allocated for transmission of a second controlchannel 602 on the subframe 608 of the first carrier 606.

The transmitter may transmit the second control channel 602 on the firstcarrier 606. The second control channel 602 may provide transmissionformat and scheduling information for a first plurality of data packetstransmitted on a first data channel 603 of the first carrier 606. Thesecond control channel 602 may be transmitted on the first carrier 606starting from the first OFDM symbol of the subframe 608. A subset ofOFDM subcarriers of the first symbol of each subframe is used by thefirst control channel, and a second subset of OFDM subcarriers of thefirst symbol of each subframe is used by the second control channel.

The transmitter may transmit the first plurality of data packets on thefirst data channel 603. The first data channel transmission may startfrom the OFDM symbol immediately after the number of OFDM symbolsallocated for the second control channel 602. For example in a givensubframe, the first, second and third symbols are used by the first andsecond control channel, and the forth to fourteenth symbols are used bythe first data channel.

The transmitter may transmit a control message 604 on the first datachannel 603 indicating that radio resources of a second data channel 605start from the first, second, third, fourth, or fifth OFDM symbol of asubset of subframes of a second carrier 607 in the plurality ofcarriers. If cross carrier scheduling is configured for the secondcontrol channel, the control message may further indicate that thesecond control channel 602 includes transmission format and schedulinginformation for a second plurality of data packets transmitted on thesecond data channel 605 of the second carrier 607. The control message604 may be transmitted once or when the radio configuration changes. Thecontrol message 604 may not be transmitted in every subframe.

The transmitter may transmit the second plurality of data packets on thesecond data channel 605. In an example embodiment, radio resources forthe second data channel 605 may start from the first OFDM symbol and endat the last OFDM symbol of each subframe 608 of the second carrier 607.The transmission format and scheduling information for the secondplurality of data packets may be transmitted on the second controlchannel 602 of the first carrier 606. The starting symbol of datachannel 605 and ePDCCH channel may be the same and may be configured bythe RRC control message.

Synchronization signal may be transmitted in subframes 0 and 5 in themiddle of the band 609 on carrier one. Synchronization signal may or maynot be transmitted in carrier two 607 depending on the second carrierconfiguration. If synchronization signal is not configured, thesynchronization signal radio resources may be allocated to the seconddata channel 605.

The first control channel 601 may be transmitted on a first subset ofthe plurality of OFDM subcarriers of the first carrier 606. Eachinstance of the first control channel 601 may indicate one of threepossible values after being decoded. The range of possible values ofeach instance of the first control channel may depend on many parametersincluding the first carrier bandwidth. For example for a givenbandwidth, the first control channel may indicate of three possiblevalues of 1, 2, or 3 symbols. The first control channel 601 istransmitted on the first OFDM symbol of each subframe 608 of the firstcarrier 606 using QPSK modulation. The first control channel 601 may becoded using a block encoder before transmission. The first controlchannel 601 may be scrambled by a transmitter ID before transmission.The transmitter ID may be for example the physical cell ID.

The second control channel 602 may be transmitted on a second subset ofthe plurality of OFDM subcarriers of the first carrier 606. The secondcontrol channel 602 may be transmitted using QPSK modulated symbols. Thesecond control channel 602 may be coded by tail biting convolutionallyencoder before transmission. The second control channel 602 may furtherprovide power control commands for uplink channels, for example powercontrol commands for physical uplink shared channel or physical uplinkcontrol channel. The OFDM subcarriers that are allocated fortransmission of the second control channel 602 may occupy the entirebandwidth of the first carrier 606. The second channel may not use theentire subcarriers allocated to it. The second control channel 602 maycarry a plurality of downlink control packets in each subframe 608 inthe plurality of subframes. Each of the plurality of downlink controlpackets may be scrambled using a radio network identifier.

The first plurality of data packets and the second plurality of datapackets may be encrypted packets. Each of the first plurality of datapackets and each of the second plurality of data packets may be assignedto a radio bearer. A first plurality of packets that are assigned to thesame radio bearer may be encrypted using an encryption key and at leastone parameter that changes substantially rapidly over time.

The control message 604 may be encrypted and may be protected by anintegrity header before it is transmitted. The control message 604 maybe transmitted by an RRC protocol. The control message 604 may furtherinclude configuration information for physical channels for a wirelessterminal. The control message 604 may set up or modify at least oneradio bearer. The control message 604 may modify configuration of atleast one parameter of a MAC layer or a physical layer. The controlmessage 604 may be an RRC connection reconfiguration message.

The control message 604 may be decrypted and its integrity header may beverified before being processed. The control message 604 may be receivedby an RRC protocol. The control message 604 may further includeconfiguration information for physical channels for the wirelessterminal. The control message 604 may set up or modify at least oneradio bearer. The control message 604 may modify configuration of atleast one parameter of a MAC layer or a physical layer. The controlmessage 604 may be an RRC connection reconfiguration message.

In an example embodiment, a prime or a non-prime carrier (equally callednon-backward compatible carrier) may include ePDCCH resources. ePDCCH isenhanced physical downlink control channel and may act as PDCCH for thenon-prime carrier or prime carrier. ePDCCH may carry schedulinginformation for downlink and uplink shared channels and may also carrierpower control information for uplink transmissions.

FIG. 7 is a diagram illustrating uplink and downlink subframes fordownlink carrier one 701, downlink carrier two 702, uplink carrier one711, and uplink carrier 2, according to an example embodiment. DLsubframe 703 is not necessary at the same time than uplink subframe 704.Radio resources 705 are allocated for PCFICH, PDCCH, and PHICH. PDCCHprovides scheduling information for downlink shared channels 706 and 707and uplink shared channels 708 and 709. PHICH provides positive ornegative acknowledgements for packets transmitted on uplink sharedchannels 708 and 709. PUCCH is transmitted on radio resources 710 and810 and may comprise: positive and negative acknowledgements for datapackets transmitted on the downlink carrier one and the downlink carriertwo; and channel state information for the downlink carrier one and thedownlink carrier two.

FIG. 8 is a block diagram illustrating an encryption mechanism accordingto an example embodiment. Data and control packets are encrypted usingEPS encryption algorithm. The encryption algorithm input parameters mayinclude a key, hyper frame number, sequence number, bearer identity,uplink or downlink direction parameter, or packet length. The controlpackets may also use an integrity mechanism that uses at least one ofthese parameters in the integrity checksum calculation process.

In an example embodiment, a first base station comprises a communicationinterface, a processor, and a memory storing instructions that, whenexecuted, cause the first base station to perform certain functions. Thebase station may transmit a control message to a wireless device. Thecontrol message may comprise an identifier for each carrier in theplurality of carriers and information identifying a carrier type foreach carrier in the plurality of carriers. The plurality of carriers maycomprise at least one backward compatible carrier and at least onenon-backward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible. The first base station maytransmit a plurality of packets to the wireless device on the at leastone non-backward compatible carrier and the at least one backwardcompatible carrier. FIG. 5, FIG. 6 and FIG. 7 show examples of abackward compatible carrier and a non-backward compatible carrier. InFIG. 5 and FIG. 6, downlink carrier 1 prime carriers 501 and 606 arebackward compatible carriers and downlink carrier 2 non-prime carrier502 and 607 are non-backward compatible carriers. In FIG. 7, DL Carrier1 is a backward compatible carrier and DL carrier 2 is a non-backwardcompatible carrier.

In another example embodiment, the base station may transmit a controlmessage (RRC message) to a wireless device. The control message maycomprise an identifier for each carrier in the plurality of carriers andinformation identifying a carrier type for each carrier in the pluralityof carriers. The plurality of carriers may comprise at least onebackward compatible carrier and at least one non-backward compatiblecarrier. The same or a different RRC message may also configure ePDCCHone or more ePDCCH configuration for one or more backward compatibleand/or non-backward compatible carrier. Common reference signal overheadof each of the at least one non-backward compatible carrier may be lowerthan common reference signal overhead of each of the at least onebackward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible. The base station may transmit aplurality of packets to the wireless device on the at least onenon-backward compatible carrier and the at least one backward compatiblecarrier.

In another example embodiment, a first base station may transmit acontrol message to a wireless device. The control message may comprisean identifier for each carrier in the plurality of carriers, informationidentifying a carrier type for each carrier in the plurality ofcarriers, and information associating at least one non-backwardcompatible carrier in the at least one non-backward compatible carrierwith a backward compatible carrier in the at least one backwardcompatible carrier. The control message may further comprise informationassociating a non-backward compatible carrier in the at least onenon-backward compatible carrier with a backward compatible carrier inthe at least one backward compatible carrier. The plurality of carriersmay comprise at least one backward compatible carrier and at least onenon-backward compatible carrier. Common reference signal overhead ofeach of the at least one non-backward compatible carrier may be lowerthan common reference signal overhead of each of the at least onebackward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible. When cross carrier scheduling isconfigured for the non-backward compatible carrier, the base station maytransmit a plurality of control messages to the wireless device on abackward compatible carrier. The plurality of control messages maycomprise scheduling information for transmission of packets on anon-backward compatible carrier associated with the backward compatiblecarrier. The plurality of control messages may be PDCCH or ePDCCHcontrol messages. The base station may transmit a plurality of packetsto the wireless device on the non-backward compatible carrier accordingto the scheduling information.

In another example embodiment, a first base station may transmit acontrol message to a wireless device. The control message may comprisean identifier for each carrier in the plurality of carriers, informationidentifying a carrier type for each carrier in the plurality ofcarriers, and information associating at least one non-backwardcompatible carrier or each non-backward compatible carrier in the atleast one non-backward compatible carrier with a backward compatiblecarrier in the at least one backward compatible carrier. The pluralityof carriers may comprise at least one backward compatible carrier, andat least one non-backward compatible carrier. Common reference signaloverhead of each of the at least one non-backward compatible carrier maybe lower than common reference signal overhead of each of the at leastone backward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible. The base station may receivechannel state information of one of the at least one non-backwardcompatible carrier from the wireless device on an uplink carrierassociated with one of the at least one backward compatible carrier. Theone non-backward compatible carrier may be associated with the onebackward compatible carrier.

In an example embodiment, a wireless device comprises a communicationinterface, a processor, and a memory storing instructions that, whenexecuted, cause the wireless device to perform certain functions. Thewireless device may receive a control message from a first base station.The control message may comprise an identifier for each carrier in theplurality of carriers and information identifying a carrier type foreach carrier in the plurality of carriers. The plurality of carriers maycomprise at least one backward compatible carrier, and at least onenon-backward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible. The wireless device may receivea plurality of packets from the first base station on the at least onenon-backward compatible carrier and the at least one backward compatiblecarrier.

In another example embodiment, a wireless device may receive a controlmessage from a first base station. The control message may comprise anidentifier for each carrier in the plurality of carriers and informationidentifying a carrier type for each carrier in the plurality ofcarriers. The plurality of carriers may comprise at least one backwardcompatible carrier and at least one non-backward compatible carrier.Common reference signal overhead of each of the at least onenon-backward compatible carrier may be lower than common referencesignal overhead of each of the at least one backward compatible carrier.The carrier type may be one of backward compatible and non-backwardcompatible. The wireless device may receive a plurality of packets tofrom the first base station on the at least one non-backward compatiblecarrier and the at least one backward compatible carrier.

In another example embodiment, a wireless device may receive a controlmessage from a first base station. The control message may comprise anidentifier for each carrier in the plurality of carriers, informationidentifying a carrier type for each carrier in the plurality ofcarriers, and information associating one non-backward compatible oreach non-backward compatible carrier in the at least one non-backwardcompatible carrier with a backward compatible carrier in the at leastone backward compatible carrier. The plurality of carriers may compriseat least one backward compatible carrier, and at least one non-backwardcompatible carrier. Common reference signal overhead of each of the atleast one non-backward compatible carrier may be lower than commonreference signal overhead of each of the at least one backwardcompatible carrier. The carrier type may be one of backward compatibleand non-backward compatible. The wireless device may receive a pluralityof control messages from the first base station on a backward compatiblecarrier. The plurality of control messages may comprise schedulinginformation for reception of packets on a non-backward compatiblecarrier associated with the backward compatible carrier. The wirelessdevice may receive a plurality of packets from the first base station onthe non-backward compatible carrier according to the schedulinginformation. In an example embodiment, the same RRC message(s) thatconfigure carriers may also configure ePDCCH resources on one or more ofthe carriers and may comprise ePDCCH configuration parameters for one ormore of the carriers.

In another example embodiment, a wireless device may receive a controlmessage from a first base station. The control message may comprise anidentifier for each carrier in the plurality of carriers, informationidentifying a carrier type for each carrier in the plurality ofcarriers, and information associating one non-backward compatiblecarrier or each non-backward compatible carrier in the at least onenon-backward compatible carrier with a backward compatible carrier inthe at least one backward compatible carrier. The plurality of carriersmay comprise at least one backward compatible carrier, and at least onenon-backward compatible carrier. Common reference signal overhead ofeach of the at least one non-backward compatible carrier is lower thancommon reference signal overhead of each of the at least one backwardcompatible carrier. The carrier type may be one of backward compatibleand non-backward compatible. The wireless device may transmit channelstate information of one of the at least one non-backward compatiblecarrier to the first base station on an uplink carrier associated withone of the at least one backward compatible carrier. The onenon-backward compatible carrier is associated with the one backwardcompatible carrier.

In example embodiments, the control message may be encrypted and may beprotected by an integrity header before it is transmitted. The controlmessage may be transmitted by an RRC protocol module. The controlmessage may further include configuration information for physicalchannels for the wireless device. The control message may set up ormodify at least one radio bearer. The control message may modifyconfiguration of at least one parameter of a MAC layer or a physicallayer. The control message may configure at least one of a physicallayer parameter, a MAC layer parameter and an RLC layer parameter. Thecontrol message may be an RRC connection reconfiguration message.Broadcast system information messages may be broadcasted on at least oneof the at least one backward compatible carrier. The control messagecomprises radio link configuration information comprising measurementconfiguration. The control message may comprise radio link configurationinformation comprising uplink channel configuration. The control messagemay comprise radio link configuration information comprising handoverparameters.

The base station may receive an RRC reconfiguration complete messagefrom the wireless device. The RRC reconfiguration complete message mayindicate that the control message is successfully processed by thewireless device. The RRC reconfiguration complete message may include anRRC transaction identifier. The RRC reconfiguration message and RRCreconfiguration complete message may be encrypted and may be protectedby an integrity header before being transmitted. The control message maybe an RRC Connection Reconfiguration message in LTE-advanced technology.The control message may modify an RRC connection. The control messagemay include an RRC transaction identifier. The control message may be anRRC connection set up message. The wireless device may transmit aresponse message after it receives the control message. The responsemessage may include a preferred PLMN ID.

The control message may configure the signal quality metric that thewireless device measures. The control message may configure measurementreporting criteria. The control message may configure cross carrierscheduling configuration. The cross carrier scheduling configuration mayassociate one non-backward compatible carrier in the at least onenon-backward compatible carrier with a backward compatible carrier inthe at least one backward compatible carrier.

The control message may comprise physical channel configuration, thephysical channel configuration may comprise cross carrier schedulingconfiguration. The control message may comprise radio resourceconfiguration. The radio resource configuration may comprise physicalchannel configuration. The carrier identifier may a carrier index. Theremay be multiple alternatives for reference signal transmission. Thecommon reference signal may not transmitted on the at least onenon-backward compatible carrier. The common reference signal may betransmitted in a pre-configured subset of the subframes on the at leastone non-backward compatible carrier. The common reference signal may betransmitted in PDCCH radio resource on the at least one non-backwardcompatible carrier. The common reference signal may be transmitted onthe at least one non-backward compatible carrier. CSI reference signalmay be transmitted on the at least one non-backward compatible carrier.CSI reference signal may be transmitted on the at least one backwardcompatible carrier. Demodulation reference signal may be transmitted onthe at least one non-backward compatible carrier. Demodulation referencesignal may be transmitted on the at least one backward compatiblecarrier.

The base station may transmit a plurality of control messages to thewireless device on a backward compatible carrier. The plurality ofcontrol messages may comprise scheduling information for transmission ofpackets on a non-backward compatible carrier associated with thebackward compatible carrier. The base station may transmit a pluralityof packets to the wireless device on the non-backward compatible carrieraccording to the scheduling information.

The plurality of control messages may be PDCCH control messages. One ofthe at least one backward compatible carrier may be a primary cellcarrier for the wireless device. The channel state information maycomprise at least CQI information, and/or rank indicator information,and/or precoding matrix indicator information. The format of the channelstate information may be configured by the control message.

In an example embodiment, base stations in a wireless network may bedirectly or indirectly connected to each other to exchange signaling anddata packets. This interface in LTE and LTE-Advanced is called X2interface. The X2 user plane interface (X2-U) may be defined betweenbase stations. The X2-U interface may provide non-guaranteed delivery ofuser plane PDUs. The transport network layer is built on IP transportand GTP-U is used on top of UDP/IP to carry the user plane PDUs. The X2control plane interface (X2-CP) may be defined between two neighbor basestations. The transport network layer may be built on SCTP on top of IP.The application layer signaling protocol may be referred to as X2-AP (X2Application Protocol). A single SCTP association per X2-C interfaceinstance may be used with one pair of stream identifiers for X2-C commonprocedures. Only a few pairs of stream identifiers may be used for X2-Cdedicated procedures. The list of functions on interface between thebase stations may include the following: mobility support, loadmanagement, inter-cell interference coordination, and data exchange.

In order to establish an association between two base stations, a firstbase station sends a first message to a second base station to initiatean association between two endpoints. The first initiation message maycomprise the following parameters: Initiate Tag, Advertised ReceiverWindow Credit, Number of Outbound Streams, Number of Inbound Streams,and an Initial Transmit Sequence Number.

Initiation Tag may be a 32-bits unsigned integer. The receiver of theinitiation message (the responding end) may record the value of theInitiate Tag parameter. This value may be placed into the VerificationTag field of every SCTP packet that the receiver of the initiationmessage transmits within this association. The Initiation Tag may beallowed to have any value except 0.

Advertised Receiver Window Credit may be 32-bits unsigned integer. Thisvalue may represent the dedicated buffer space, in number of bytes, thesender of the initiation message may be reserved in association withthis window. During the life of the association, this buffer space maynot be lessened (i.e., dedicated buffers taken away from thisassociation); however, an endpoint may change the value of window creditit sends in a packet. Number of Outbound Streams may be 16 bits unsignedinteger. It may define the number of outbound streams the sender of thisinitiation message wishes to create in this association. Number ofInbound Streams may be 16 bits unsigned integer. It may define themaximum number of streams the sender of this initiation message mayallow the peer end to create in this association. There may be nonegotiation of the actual number of streams but instead the twoendpoints may use the min(requested, offered). Initial Transmit sequencenumber may be 32-bits unsigned integer. It may define the initialtransmit sequence number that the sender may use. This field may be setto the value of the Initiate Tag field.

The second base station transmits an initiation acknowledgement messageto acknowledge the initiation of an SCTP association with the first basestation. The parameter part of the initiation acknowledgement messagemay be formatted similarly to the initiation message. It may use twoextra variable parameters: The State Cookie and the UnrecognizedParameter. Initiate Tag may be a 32-bits unsigned integer. The receiverof the initiation acknowledgement message may record the value of theInitiate Tag parameter. This value may be placed into the VerificationTag field of every SCTP packet that the initiation acknowledgementmessage receiver transmits within this association. Advertised ReceiverWindow Credit may be a 32-bits unsigned integer. This value mayrepresent the dedicated buffer space, in number of bytes, the sender ofthe initiation acknowledgement message has reserved in association withthis window. During the life of the association, this buffer space maynot be lessened (i.e., dedicated buffers taken away from thisassociation).

Number of Outbound Streams may be 16-bits unsigned integer. It maydefine the number of outbound streams the sender of this initiationacknowledgement message wishes to create in this association. Number ofInbound Streams may be a 16-bits unsigned integer. It may define themaximum number of streams the sender of this initiation acknowledgementmessage allows the peer end to create in this association. There may notbe negotiation of the actual number of streams but instead the twoendpoints will use the min(requested, offered). Initial TransmitSequence Number (TSN) may be a 32-bits unsigned integer. It defines theinitial TSN that the initiation acknowledgement message sender may use.This field may be set to the value of the Initiate Tag field. The statecookie parameter may contain the needed state and parameter informationrequired for the sender of this initiation acknowledgement message tocreate the association, along with a Message Authentication Code (MAC).Unrecognized Parameter may be returned to the originator of theinitiation message when the initiation message contains an unrecognizedparameter that has a value that indicates it should be reported to thesender. This parameter value field may contain unrecognized parameterscopied from the initiation message complete with Parameter Type, Length,and Value fields.

When sending an initiation acknowledgement message as a response to aninitiation message, the sender of initiation acknowledgement message maycreate a State Cookie and sends it in the State Cookie parameter of theinitiation acknowledgement message. Inside this State Cookie, the sendermay include a message authentication code, a timestamp on when the StateCookie is created, and the lifespan of the State Cookie, along with theinformation needed for it to establish the association. The followingsteps may be taken to generate the State Cookie: 1) Create anassociation transmission control block (TCB) using information from boththe received initiation and the outgoing initiation acknowledgementmessages, 2) In the TCB, set the creation time to the current time ofday, and the lifespan to the protocol parameter to a pre-determinednumber, 3) From the TCB, identify and collect the minimal subset ofinformation needed to re-create the TCB, and generate a MAC using thissubset of information and a secret key, and 4) Generate the State Cookieby combining this subset of information and the resultant MAC.

After sending the initiation acknowledgement with the State Cookieparameter, the sender may delete the TCB and any other local resourcerelated to the new association, so as to prevent resource attacks. Thehashing method used to generate the MAC is strictly a private matter forthe receiver of the initiation message. The use of a MAC is used toprevent denial-of-service attacks. The secret key may be random. It maybe changed reasonably frequently, and the timestamp in the State Cookiemay be used to determine which key should be used to verify the MAC. Animplementation may make the cookie as small as possible to ensureinteroperability.

The first base station may transmit at least one third message to thesecond base station. One of the at least one third message may becookie-echo message. The cookie-echo message may be used during theinitialization of an association. It may be sent by the initiator of anassociation to its peer to complete the initialization process. Thismessage may precede any transport packet message sent within theassociation, but may be bundled with one or more data transport packetin the same packet. This message may contain the exact cookie receivedin the State Cookie parameter from the previous initiationacknowledgement message. The type and flags of the cookie-echo may bedifferent than the cookie parameter. An implementation may make thecookie as small as possible to ensure interoperability. A Cookie Echomay not contain a State Cookie parameter, instead, the data within theState Cookie's Parameter Value becomes the data within the Cookie Echo'sChunk Value. This may allow an implementation to change only the first 2bytes of the State Cookie parameter to become a cookie echo message. Thefirst base station may transmit at least one application protocolmessage in cookie echo message. Or the base station may choose totransmit application protocol messages after the association is completeand do not include application protocol messages in cookie-echo message.This is an implementation option.

The application protocol message may receive a cookie-ack message fromthe second base station. This message may be used only during theinitialization of an association. It may be used to acknowledge thereceipt of a cookie-echo message. This message may precede any data sentwithin the association, but may be bundled with one or more data packetsin the same SCTP packet. The second base station may transmit at leastone application protocol message in cookie ack message. Or the basestation may choose to transmit application protocol messages after theassociation is complete and may not include application protocolmessages in cookie-ack message. This may be an implementation option.

After the initiation and initiation acknowledgement messages aretransmitted, the first base station or the second base station maytransmit an X2 setup message to set up an X2 application interface. Thefirst base station or the second base station may wait until theassociation is complete to set up an X2 application interface. Eitherfirst base station or second base station may start the set up of an X2application. The purpose of the X2 Setup procedure may be to exchangeapplication level configuration data needed for two base stations tointeroperate correctly over the X2 interface. This procedure may eraseany existing application level configuration data in the two nodes andreplace it by the one received. This procedure may also reset the X2interface like a reset procedure would do.

A first base station or second base station may initiate the procedureby sending the X2 set up request message to a candidate base station.The candidate base station may reply with the X2 set up responsemessage. The initiating base station may transfer the list of servedcells. The candidate base station may reply with the complete list ofits served cells in the reply.

The X2 set up request message may include the following informationabout the originator of the message: a global base station identifier,the information about the served cells, and a GU group identifier list.GU Group identifier list is the pools to which the base station belongsto. Each row in this list may include the PLMN ID and MME groupIdentifier. The information about each served cell may includeinformation about the served cell configurations. It may also includethe list of neighbor cells of the served cell including: Cell GlobalIdentifier of the neighbor cell, Physical Cell Identifier of theneighbor cell, frequency. The served cell information may include atleast one of the following parameters: Physical Cell ID, global cellidentifier, Tracking Area Code, at least one Broadcast PLMN, FDDinformation (uplink and downlink frequencies, uplink and downlinktransmission bandwidth), TDD information (transmission frequency,subframe assignment, special subframe information, special subframepattern, cyclic prefix for downlink and uplink), number of antennaports, PRACH Configuration, MBSFN Subframe Info (Radio frame AllocationPeriod, Radio frame Allocation Offset, Subframe Allocation), and CSGidentifier. The X2 set up request message may also include informationidentifying the served cell downlink or/and uplink carrier type. Thisinformation may be included explicitly or implicitly in the served cellconfiguration. The carrier type here may be a first, second, or thirdcarrier type. For example, carrier type may be broadly identified asbackward compatible carrier and non-backward compatible carriers. Inother example embodiment, the categorization may be different. Eachserved cell includes a downlink carrier. The carrier types may be calledusing various names such as data carriers, data cells, control carriers,control cells, primary cells, primary carriers, secondary cells,secondary carriers, or other example names. Each cell includes adownlink carrier and may or may not include an uplink carrier. A celltype may implicitly indicate a carrier type in the example embodiments.The backward compatible and non-backward compatible are functionalcharacteristics of the carriers and may not be reflected in the carriertypes names. The carrier type may not be explicitly indicated in themessages, but this information may be implicitly obtained from themessages. For example, an X2 set up request, may identify cell types A,B, C, and D. Cell type A, B, and C may include backward compatiblecarrier(s), and cell type D may include non-backward compatiblecarrier(s). The information about which carrier is backward compatibleand which carrier is not backward compatible is implicitly determinedbased on the definition of cell types A, B, C, and D. For example, abackward compatible carrier may be used by all wireless devices ofrelease 11 and beyond. But a non-backward compatible carrier may be usedby wireless devices of release 12 and beyond. Another example of carriertypes may be synchronized carrier, segment carrier, non-synchronized newcarrier type (NCT), standalone NCT, non-standalone NCT, and/or the like.

X2 set up response messages may include most or all of the fields of theX2 set up request message characterizing the base station that istransmitting the message. After two base stations exchange X2 set uprequest and response message, each base station may be aware of theother base station configurations including information about itsserving cells. This information may be used to perform various functionsperformed by X2 interface including handover signaling and management,load management, and interference coordination.

In an example embodiment, a first base station comprises a communicationinterface, a processor, and a memory storing instructions that, whenexecuted, cause the first base station to perform certain functions. Thebase station may receive a second application protocol message from asecond base station in the plurality of base stations. The secondapplication protocol message may comprise a unique identifier of thesecond base station, cell identifier for each of the at least onebackward compatible carrier, and information identifying a carrier typefor each carrier in the plurality of carriers. The second base stationmay comprise a plurality of carriers comprising at least one backwardcompatible carrier, and at least one non-backward compatible carrier.The carrier type may be one of backward compatible and non-backwardcompatible. The information in the application protocol messages may beemployed, at least in part, when the base stations are communicatingwith other. For example, a base station may make a handover decision.The first base station may operate a wireless device handover based, atleast in part, on information in the second application protocolmessage. Handover signaling and messages may employ at least in part theinformation in the application protocols (e.g. setup message and setupresponse message).

In an example embodiment, a first base station may receive a secondapplication protocol message from a second base station. The secondapplication protocol message may comprise a unique identifier of thesecond base station, cell identifier for each of the at least one firsttype carrier, and information identifying a carrier type for eachcarrier in said plurality of carriers. The second base station comprisesa plurality of carriers comprising at least one first type carrier, andat least one second type carrier. The carrier type may be one of firsttype and second type. The base station may operate a wireless devicehandover based, at least in part, on information in the secondapplication protocol message.

In another example embodiment, a first base station may receive a secondapplication protocol message from a second base station in the pluralityof base stations. The second application protocol message may comprise aunique identifier of the second base station, at least one MME groupidentifier, cell identifier for each of the at least one backwardcompatible carrier, and information identifying a carrier type for eachcarrier in the plurality of carriers. The second base station maycomprise a plurality of carriers comprising at least one backwardcompatible carrier, and at least one non-backward compatible carrier.Common reference signal overhead of each of the at least onenon-backward compatible carrier may be lower than common referencesignal overhead of each of the at least one backward compatible carrier.The carrier type may be one of backward compatible and non-backwardcompatible. The first base station may operate a wireless devicehandover based, at least in part, on information in the secondapplication protocol message.

In another example embodiment, a first base station may transmit a firstmessage to initiate an association between the first base station and asecond base station in the plurality of base stations. The first messagemay comprise a first initiation tag. The first base station may receivea second message from the second base station. The second message maycomprise a second verification tag, a second initiation tag, and a firststate parameter. The second verification tag may be equal to the firstinitiation tag. A first state parameter may comprise at least oneparameter related to operational information of the association, and amessage authentication code generated as a function of a private key.The first base station may transmit at least one third message to thesecond base station. The at least one third message may comprise a firstverification tag, and a parameter comprising the first state parameter.The first verification tag may be equal to the second initiation tag.The first base station may receive at least one fourth message from thesecond base station. The at least one fourth message may comprise anacknowledgement for the receipt of the parameter and a secondapplication protocol message. The second application protocol messagemay comprise a unique identifier of the second base station, at leastone MME group identifier, cell identifier for each of the at least onebackward compatible carrier, and information identifying a carrier typefor each carrier in the plurality of carriers. The second base stationmay comprise a plurality of carriers comprising at least one backwardcompatible carrier and at least one non-backward compatible carrier.Common reference signal overhead of each of the at least onenon-backward compatible carrier may be lower than common referencesignal overhead of each of the at least one backward compatible carrier.The carrier type may be one of backward compatible and non-backwardcompatible. The first base station may operate a wireless devicehandover using the association and based, at least in part, oninformation in the at least one fourth message.

In example embodiments, the first initiation tag value may be a selectedin the first base station using a pseudo-random process. The secondinitiation tag value may be selected in the second base station using apseudo-random process. The first message may further comprise a firstbase station transport address and a second base station transportaddress. The first message may further comprise a first advertisedreceiver window credit representing a dedicated buffer space that thefirst base station reserves for a window of received packets from thesecond base station. The first message may further comprise a firstinitial transmission sequence number that the first base station usesfor transmission of data segments. The first initial transmissionsequence number may be equal to the first initiation tag.

The second message may further comprise the first base station transportaddress and the second base station transport address. The secondmessage may further comprise a second advertised receiver window creditrepresenting a dedicated buffer space that the second base stationreserves for a window of received packets from the first base station.The second message may further comprise a second initial transmissionsequence number that the second base station uses for transmission ofdata chunks. The second initial transmission sequence number may beequal to the second initiation tag. The at least one third message mayfurther comprise the first base station transport address and the secondbase station transport address. The at least one third message mayfurther comprise a transmit sequence number, a stream identifier, astream sequence number.

The at least one fourth message may further comprise a transmit sequencenumber, a stream identifier, and a stream sequence number. The secondbase station may place the first initiation tag in the verification tagof every transport layer packet that it transmits to the first basestation within the association. The first base station may place thesecond initiation tag in the verification tag of every SCTP packet thatit transmits to the second base station within the association. Theassociation may be an SCTP association. The at least one fourth messagemay further comprise the first base station transport address and thesecond base station transport address. The second application protocolmessage may be an X2-Application Protocol Setup Request message. Thesecond application protocol message may be an X2-Application ProtocolSetup Response message. The at least one third message may furthercomprise an X2-Application Protocol Setup Request message. The at leastone third message may further comprise an X2-Application Protocol SetupResponse message.

The first state parameter may further comprise a timestamp on when thefirst state parameter is created. The first state parameter may furthercomprise the lifespan of the first state parameter. The messageauthentication code may further be a function of at least one parameterrelated to operational information of the association. The at least onethird message may further comprise a first application protocol message.The first application protocol message may comprise a unique identifierof the first base station, at least one MME group identifier, cellidentifier for each of the at least one backward compatible carrier,information identifying a carrier type for each carrier in the pluralityof carriers. The first base station may comprise a plurality of carrierscomprising at least one backward compatible carrier and at least onenon-backward compatible carrier. The carrier type may be one of backwardcompatible and non-backward compatible.

The first verification tag and the second verification tag in theassociation may not change during the life time of the association. Anew verification tag value may be used each time the first base stationor the second base station tears down and then reestablishes anassociation with the same node. The operational information comprises atleast one of the following: a parameter in the first message, aparameter in the second message, a state of the association, aconfiguration parameter of the first base station, and a configurationparameter of the second base station. The first message and the secondmessage may further comprise a checksum for packet validation. The firstbase station transport address and the second base station transportaddress may comprise an IP address and a port address. The secondapplication protocol message may further comprise cell identifier foreach of the at least one non-backward compatible carrier. The secondapplication protocol message may further comprise informationidentifying for each of the at least one non-backward compatiblecarrier, a corresponding backward compatible carrier.

There are various alternative options for transmitting reference signalon downlink carriers. The at least one backward compatible carrier maybroadcast a common cell reference signal and the at least onenon-backward compatible carrier may not broadcast the common cellreference signal. The common reference signal may not be transmitted onthe at least one non-backward compatible carrier. The common referencesignal may be transmitted in a pre-configured subset of the subframes onthe at least one non-backward compatible carrier. The common referencesignal may be transmitted in PDCCH radio resource on the at least onenon-backward compatible carrier. The common reference signal may betransmitted on the at least one non-backward compatible carrier. CSIreference signal may be transmitted on the at least one non-backwardcompatible carrier. CSI reference signal may be transmitted on the atleast one backward compatible carrier. Demodulation reference signal maybe transmitted on the at least one non-backward compatible carrier.Demodulation reference signal maybe transmitted on the at least onebackward compatible carrier.

The first message may further comprise a first number of outboundstreams that the first base station intend to create and a first maximumnumber of inbound streams that the first base station allows the secondbase station to create. The second message may further comprise a secondnumber of outband streams that the second base station intend to create,a second maximum number of inbound streams the second base stationallows the first base station to create. The second number of outbandstreams is smaller than or equal to the first maximum number of inboundstreams. The first base station may further select a number equal orlower than the minimum of the first number of outband streams and thesecond maximum number of inbound streams as the number of outbandstreams for the first base station.

A new downlink carrier type for carrier aggregation may be introduced.Such a carrier may not be initially defined for standalone operation.The UL PCC may contain the PUCCH. The UL SCC linked to (by fixed duplexdistance in FDD) the new DL SCC type may not have any PUCCH region. InRel-10, the PCell configuration may be UE-specific which may bebeneficial, e.g., to balance the load among the serving cells in theeNodeB. It may be possible that an UL CC has a PUCCH for some UE. Withthe new downlink carrier type, this may be achieved and the consequenceof the new downlink carrier type is that the associated UL CC may be aPUCCH-less carrier. A new DL carrier type may improve the spectralefficiency. The extra RBs previously being used for the PUCCH may beavailable for PUSCH transmission in the associated UL CC. A requirementfor spectrally efficient PUSCH transmission may be that the eNodeB mayhave the means to leverage on the frequency selectivity of the channelfor the scheduling and link adaptation, which may be used in case ofcarrier aggregation, where the link conditions may be good and localizedtransmissions may be preferred. The PUCCH-less carrier may not be an ULPCC and thus may carry transmissions from UEs being configured with ULcarrier aggregation. Those UEs may not be power limited and the UL linkconditions may be expected to be favorable.

An ePDCCH may be configured for legacy carriers and/or new typecarriers. An ePDCCH may allow frequency domain scheduling and beamforming gains for control signaling without increasing the RS overhead.Cross carrier scheduling may or may not be used for scheduling the newcarrier type using legacy or ePDCCH.

The new type carrier may be associated with a backward compatiblecarrier. In one example implementation, the new carrier may not exist asstand-alone and may exist as an SCell by carrier aggregation with abackward compatible carrier. The new type carrier itself may be acomponent carrier in the perspective of the carrier aggregation. ThePDSCH in the new type carrier may be scheduled independently from theother aggregated carriers with independent HARQ processes. In an exampleembodiment, regarding RB allocation algorithms for the PDSCH in the newtype carrier, legacy RB allocation algorithms may be used. In the newtype carrier, PDSCH may be scheduled independently from the otheraggregated carriers with independent HARQ processes. PDSCH in the newtype carrier may be cross-carrier scheduled by the other aggregatedcarrier. E-PDCCH may be supported in the new type carrier, PDSCH in thenew type carrier may be scheduled by E-PDCCH in the new type carrieritself.

In case of the cross-carrier scheduling in Rel-10 carrier aggregation,PDSCH starting position of an SCell may be RRC-signaled to the UE. Eventhough the new type carrier may not transmit PDCCHs in its starting OFDMsymbol(s) in a subframe, the eNB may configure the starting OFDMsymbol(s) in a subframe of the new type carrier in order to blank someof OFDM symbols for the purpose of interference coordination, forexample, in some HetNet scenarios where one cell uses legacy PDCCH andanother cell does ePDCCH. Therefore, ePDCCH and PDSCH starting positionof a new type carrier may be RRC signaled to the UE. The new typecarrier may not carry the legacy PDCCH signals, the RRC signaling may beable to indicate the very first OFDM symbol (ie. value 0) in a subframeas the PDSCH starting position. Legacy PDCCH may not be present on thenew carrier, the scheduling may be done through one of the following twoways: a) Cross-carrier scheduling from the associatedbackward-compatible carrier: this may raise some concern on the PDCCHcapacity on the associated carrier. b) ePDCCH: ePDCCH may be used on thenew carrier type so as to improve the PDCCH capacity and provideinterference coordination on the control channel. It may alleviate thecapacity issue on the associated carrier compared to the previousoption.

If cross-carrier scheduling is used, there may be no need for PHICH (andPCFICH) on the new carrier, because the HARQ-ACK feedback may be sent onthe associated backward-compatible carrier. If ePDCCH is used, thelegacy PHICH may be used on the carrier, or a new design may be neededfor PHICH in order to achieve similar interference coordinationcapability on the frequency domain for PHICH. The PCFICH information maybe provided semi-statically for cross-carrier scheduling cases.

A new carrier type may give the eNodeB larger flexibility in controllingthe effective bandwidth of the carrier. An ePDCCH with FDM extension inthe PDSCH region that may be located on the new carrier and that itsresources would be configurable by the eNodeB. Other control channelsmay reside on the legacy carrier. Still, the other control channels(PCFICH, PHICH) or their enhancements may become needed on the newcarrier, at least eventually if the carrier supports stand-aloneoperation.

The frequency resources used for the control channels may beconfigurable. For example, if a carrier contains a control region in thebeginning OFDM symbols of the subframe, similar to a legacy carrier,such a control region may be configurable in its frequency resourceoccupancy (RBs, DVRBs etc.). The additional downlink carrier type mayhave means for controlling the frequency resources of its controlchannels.

One way to improve the spectral efficiency may be to reduce the PDCCHoverhead. The overhead of the downlink may be reduced with some form ofjoint encoding of information fields in the PDCCHs associated with thelegacy carrier and the new carrier type. For example, the main savingsmay be due to using 1 CRC, no carrier indicator field and 1 HARQ processID. The other information fields may be duplicated for the two carriers.The additional carrier type may be deployed to fill out spectrum thatmay not commensurate with the Rel-8 channel bandwidths. Such allocationsmay be contiguous frequency blocks with bandwidths below 20 MHz. Ascenario may be when the additional carrier type is contiguouslydeployed next to the legacy carrier. In that situation, the overhead maybe significantly reduced by joint encoding but not duplicating anyinformation fields.

In an example embodiment, a network may comprise a plurality of basestations. A first base station may receive at least one message from asecond base station in the plurality of base stations. The second basestation may comprise one or more downlink carriers, each comprising aplurality of downlink resource blocks. In another example embodiment,the first base station may receive the at least one message from an OAMproviding configuration information to the first base station. The atleast one message may comprise a plurality of parameters correspondingto a physical downlink control channel resource configurationinformation. The plurality of parameters for example may comprise: oneor more frequency resource parameters in terms of resource blocks and/orone or more subframe parameters identifying a subset of subframes.

If the at least one message is received from the second base station,the plurality of parameters may provide information about radioresources that may be used by ePDCCH of a cell in the second basestation. In other word, ePDCCH of the cell may employ a subset of radioresources identified by the at least one message. The second basestation may provide this information for each of its cells. In anotherembodiment, the second base station may provide this information for asubset of its cells. In another embodiment, this information may beincluded as cell parameters in the application protocol message for eachcell or cells with a configured ePDCCH. Alternatively, it may beprovided in an information element and may be applicable to cells thatmay be potentially configured with ePDCCH.

If the at least one message is received from the OAM, the plurality ofparameters may provide information about radio resources that may beused by ePDCCH of a cell in the first base station receiving the messagefrom OAM. In other word, ePDCCH of the cell may employ a subset of radioresources identified by the at least one message. The OAM may providethis information for each of the first base station cells. In anotherembodiment, the OAM may provide this information for a subset of cells.In another embodiment, this information may be included as cellparameters in the message for each cell or cells with a configuredePDCCH. Alternatively, it may be provided in an information element andmay be applicable to cells that may be potentially configured withePDCCH.

According to some aspect of an example embodiment, one or more frequencyresource parameters in terms of resource blocks may be provided in theform of a bitmap indicating the resource blocks employed or employableto ePDCCH. For example, a bitmap with the length of 110 bits mayindicate which of the resource blocks in a 110 bits resource blocks of acell may be allocated to ePDCCH. In another example, one or morefrequency resource parameters may be provided in the form of a set ofpre-defined indexes (each index identifying a pre-defined set ofresource blocks), or a list of at least one (starting offset,bandwidth). In another example embodiment the message may provide ePDCCHconfiguration parameters that may be configured for UEs, according theePDCCH configuration parameters in the RRC messages (RRC ePDCCHconfiguration parameters are disclosed in this specification).

The plurality of parameters may comprise a starting time in subframes ofa cell or a subset of subframes of the cell. The plurality of parametersfor example may comprise beamforming information for ePDCCH for examplecodebook information, codebook index information, and/or the like. Theplurality of parameters may comprise one or more subframe parameters forexample one or more subframe parameters identifying a subset ofsubframes. For example, in the form of a bitmap with length 20, 40, 70for a cell. The bitmap may indicate which subframe of a cell may includeePDCCH resources. The plurality of parameters may indicate radioresources that aggregated ePDCCH radio resources of a cell for UEs mayuse in the second base station.

In an example embodiment, the message(s) may be application protocolmessage(s) received from a second base station by the first basestation. The message(s) provide ePDCCH radio resource configuration ofthe cell(s) of the second base station to the first base station. Thebase station may receive ePDCCH configuration parameters fromneighboring base station(s). The application protocol message forexample may be a setup message, a setup response message, eNBconfiguration update, eNB configuration update ACK, a load informationmessage, and/or an invoke message. The setup and setup response messagesmay be transmitted when the X2 connection is set up at the applicationprotocol level. The load message may transmitted regularly,periodically, and/or when needed. ePDCCH radio resource configurationparameters may be provided along with other cell parameters in theapplication protocol message for each cell. For example, a setup orsetup response message may optionally provide this information for acell (carrier) along with other cell parameters as indicated in thisdisclosure. In another example, the load message may include thisinformation along with other information of a cell such as Cell ID, ULInterference Overload Indication, Relative Narrowband Tx Power (RNTP),ABS Information, Invoke Indication, and/or the like. A load informationmessage may optionally include some of these parameters and mayoptionally include ePDCCH radio resource parameters for a cell.

In an example embodiment, the message(s) may be received from OAM. Themessages may provide radio resources applicable for ePDCCH of cells ofthe first base station. In other word, the base station may configureePDCCH of cells within the radio resources provided by OAM.

The first base station may transmit at least one RRC message toconfigure ePDCCH resources for at least one of the cells of the firstbase station. In an example embodiment, the configuration parameters ofePDCCH may be within the range of radio resources identified by OAMmessage. In an example embodiment, the configuration parameters ofePDCCH may be configured so that ePDCCH of the first base station maynot overlap (or may have reduced overlap) with neighboring basestation(s) ePDCCH radio resources. The neighboring base station may bean interference aggressor base station. This configuration may reduceinterference on ePDCCH. A base station receiving ePDCCH resources thatis potentially employed for ePDCCH configuration in neighboring cells,may configure ePDCCH resources of its cells to reduce inter-cellinterference on ePDCCH. In an example embodiment, an aggressor cell mayprovide ePDCCH resources of its cells to victim base stations. Victimbase stations may use this information in configuring ePDCCH resources.

The first base station may select at least one transmission parameter ofa first downlink control channel (for example ePDCCH) and/or a firstdownlink data channel of the downlink carrier of the first base station.The selection may be based, at least in part, on physical downlinkcontrol channel resource configuration information received from anotherbase station or from OAM. The first base station may transmit schedulingpackets on the first downlink control channel. The scheduling packetsmay comprise scheduling information for packets transmitted on the firstdownlink data channel. In an example embodiment, the selection isperformed to reduce inter-cell interference. In an example, theselection is performed to reduce overlap of radio resources between thefirst downlink control channel (first ePDCCH) and the second downlinkcontrol channel of a neighboring base station (second ePDCCH of forexample the second base station). The selection may be performed toreduce and/or eliminate the overlap of ePDCCH resources between twocells of base stations below a threshold.

The first base station may transmit a packet comprising acknowledgementfor the receipt of the at least one message. The second physicaldownlink control channel may be ePDCCH and may carry schedulinginformation for packets transmitted on a downlink shared channel and/oran uplink shared channel. The second physical downlink control channelmay carry power control commands for wireless devices transmittinguplink on an up shared channels.

According with an aspect of the disclosed embodiments, RNTP included inthe Load Information message may be used to exchange information abouttransmit power for Physical Resource Blocks (PRBs) used for datachannels, in order to assist carrier selection for users stronglyinterfered by macro cell. RNTP reporting mechanisms may enable an firsteNB to indicate to another eNB the RNTP threshold the first eNB mayprefer to receive a report on physical resource block powers. Forexample, the first eNB may send the recommended transmit power and/orexpected power reduction to another eNB, to achieve protected resources.In another example, the first eNB may indicate to another eNB toincrease or decrease the used RNTP threshold.

Support of frequency-domain ICIC may require some ePDCCH configurationinformation exchange between two base stations X2 interface. This mayallow configuring ePDCCH (specially for victim eNBs) in frequencyresource with low interference. Information exchange between two eNBsmay be needed for the case where ePDCCH transmission in the victim cellneeds to be protected from the interference caused by the aggressorcell. An ePDCCH configuration is performed by RRC layer semi-statically.It is expected that eNB does not change ePDCCH configuration frequentlyfor example every frame or a couple of frames. The aggressor eNB mayindicate the victim cell of the set of resources in which the victimcell can expect low inter-cell interference or high inter-cellinterference. The victim cell may employ this information in configuringdownlink channels in a way that it uses low interference resource blocksand reduces high interference resource blocks. LTE system may employRelative Narrowband Tx Power for frequency-domain ICIC of PDSCH. By RNTPmessage, the aggressor eNB may indicate that set of PRBs in which its DLtransmission power will be kept below a threshold for a cell.

RNTP may be employed to reduce interference in ePDCCH radio resources.RNTP for a cell may be in the form of a bitmap. Each position in thebitmap may represent a nPRB value (i.e. first bit=PRB 0 and so on), forwhich the bit value represents RNTP (nPRB). Value 0 may indicate “Tx notexceeding RNTP threshold” and Value 1 may indicates “no promise on theTx power is given”. RNTP threshold may be included in the same message.The message may also include Number Of Cell-specific Antenna Ports forcell specific reference signals. The victim may transmits ePDCCH on thePRBs for which the aggressor cell may transmit a DL transmission powerlower than RNTP threshold. In an example embodiment, a base station mayemploy RNTP information received from the neighboring base stations toconfigure ePDCCH for the UEs in the coverage area. A base station mayconfigure ePDCCH resources in RBs that aggressor base station may nottransmit power higher than RNTP. This may reduce interference on ePDCCHresources of a cell.

In another example embodiment, an information element may bespecifically defined for indicating of PRBs with low transmission powerfor the purpose of ePDCCH ICIC. In this information element, eNB mayindicate a bitmap determining resource blocks that may not be used in asemi-static fashion by an eNB. The victim eNB may use that informationfor ePDCCH configuration. The aggressor cell eNB may send, for example abitmap as a subset of RNTP, such that the PRBs indicated by this bitmapmay remain as the low-power resource in a semi-static manner. Thisinformation may be used for ePDCCH configuration. In another exampleembodiment, RNTP bitmap may be extended to include both legacy RNTPinformation and also information of resource blocks that may remainbelow a power threshold in semi-static basis. RNTP may include aninformation element for each resource block. A first value of theresource block may determine that the resource block may be at low powerfor a longer duration (semi-static configuration) and a second value mayindicate that the RNTP has low or high power. Victim base station mayuse the semi-static information for ePDCCH configuration.

According with an aspect of the disclosed embodiments, providinginter-eNB assistance may be beneficial to enhance the selection ofresources protected from interference, while mitigating interferencewith available ICIC mechanisms for those users. An eNB may informneighbour eNBs about DL interference problems on a carrier X, both indata and control regions, and exchanges the information about Pcell vs.SCell carrier loading. The neighbour eNB may use this information whendeciding on the assignment of a UE PCell and SCell(s), to achieveresource protection: in reaction to high DL interference indication,eNBs may allocate users' PCells of UE to different carriers andreallocations may be limited to SCell reconfigurations. Upon receivingthe indication of interference problems, the peer eNB may for examplereduce the number of users using carrier X (e.g. by de-activating SCellson carrier X), or reduce the transmission power on carrier X, tomitigate interference in the data region, as well as may reduce itstransmission power for the control channel region on carrier X (e.g.using cross-carrier scheduling for carrier X, such that PDCCH schedulinggrants for carrier X are send from other carriers). Knowing in additionthe loading in terms of Pcell and Scell may provide information to aneNB to decide on the assignment of a UE PCell and SCell(s), e.g. whenneighbour cells mainly use carrier 1 for PCell, the eNB can selectcarrier 1 more for SCell of its users, which allows a quickdeactivation.

According with an aspect of the disclosed embodiments, neighbouring basestation may exchange information about Pcell vs. SCell carrier loadingover X2, interference indication for data channels over X2, and/orinterference indication for control channels over X2 interface. Theindication about data interference problem on a given carrier may be asingle binary message, or may provide higher level of granularity toindicate more information on the data channel interference problems. Ifthe peer eNB for some reasons is not able to take actions for reducingthe interference on carrier X, it may inform the initiating eNB aboutthe problem. The PCell/SCell carrier load may be implemented as anextension of the Resource Status Report Initiation and Resource StatusReport procedures, e.g. in a form of number of users for whom thecarrier is PCell or SCell. DL control channel interference on a givencarrier may be estimated based on existing mechanisms (no impact on theUE). For example, an eNB may consider a UE is suffering high DLinterference in control channels in case it does not respond in largeratio as expected to control information, like scheduling grants. Thecontrolling eNB can take this into account and exchange the information,if requested, with its neighbours to improve the PCell and SCellselection.

According with an aspect of the disclosed embodiments, radio channelresources may be preconfigured in a way among macro and pico cells toproperly coordinate for carrier-based ICIC. The neighbour eNB may usethis information when deciding on the assignment of a UE PCell andSCell(s) for users suffering from strong macro interference in aproactive manner. So for example if there are two carriers, one of whichprotected from interference, that carrier can be selected as Pcell inthe pico cell to convey scheduling information and data to userssuffering from strong interference from macro, while the other carriermay be used as Scell for the same users by the pico. OAM may provide theconfiguration for protected PDCCH carrier component(s) to involved eNBs.

According with an aspect of the disclosed embodiments, the informationabout the configuration of protected resources may be exchanged betweeneNBs over X2 interface, aiming for a consistent configuration toproperly coordinate for carrier-based ICIC. The neighbour eNB may usethis information when deciding on the assignment of a UE PCell andSCell(s) for users suffering from macro interference. So for example ifthere are two carriers, one of which protected from interference, thatcarrier can be selected as Pcell in the pico cell to convey schedulinginformation and data to users suffering from strong interference frommacro, while the other carrier can be used as Scell for the same usersby the pico. The macro eNB may request to report loading statusinformation to monitor and further tune the power allocation of theprotected resources. The eNB needing assistance can send an InvokeIndication to the assisting node to receive information about allocatedresources in the frequency domain.

According with an aspect of the disclosed embodiments, information aboutthe configuration of protected PDCCH carrier component(s) may beexchanged among eNBs. Protected PDCCH carrier component(s) may be chosenby eNB(s) and information is exchanged via X2 whenever the cross-carrierscheduling is enabled. PCell and SCell information may be exchangedbetween base stations. In another example embodiment, OAM may provideprotected PDCCH carrier component(s) preference list to each eNB, and/orePDCCH information to the eNB. The eNB may choose PDCCH CC(s) or ePDCCHconfiguration parameters according to received parameters. An eNB mayexchange the information through X2, for example, whenever thecross-carrier scheduling is enabled or whenever ePDCCH is configured. Inan example embodiment, the set for protected carrier component(s) mayconfigured in the macro and signalled via the X2 interface to the pico.Whenever cross scheduling is used to convey scheduling information touser strongly interfered by macro cell, the pico may configure UE Pcellfrom this protected set.

According to some of the various aspects of embodiments, the packets inthe downlink may be transmitted via downlink physical channels. Thecarrying packets in the uplink may be transmitted via uplink physicalchannels. The baseband data representing a downlink physical channel maybe defined in terms of at least one of the following actions: scramblingof coded bits in codewords to be transmitted on a physical channel;modulation of scrambled bits to generate complex-valued modulationsymbols; mapping of the complex-valued modulation symbols onto one orseveral transmission layers; precoding of the complex-valued modulationsymbols on layer(s) for transmission on the antenna port(s); mapping ofcomplex-valued modulation symbols for antenna port(s) to resourceelements; and/or generation of complex-valued time-domain OFDM signal(s)for antenna port(s).

Codeword, transmitted on the physical channel in one subframe, may bescrambled prior to modulation, resulting in a block of scrambled bits.The scrambling sequence generator may be initialized at the start ofsubframe(s). Codeword(s) may be modulated using QPSK, 16QAM, 64QAM,128QAM, and/or the like resulting in a block of complex-valuedmodulation symbols. The complex-valued modulation symbols for codewordsto be transmitted may be mapped onto one or several layers. Fortransmission on a single antenna port, a single layer may be used. Forspatial multiplexing, the number of layers may be less than or equal tothe number of antenna port(s) used for transmission of the physicalchannel. The case of a single codeword mapped to multiple layers may beapplicable when the number of cell-specific reference signals is four orwhen the number of UE-specific reference signals is two or larger. Fortransmit diversity, there may be one codeword and the number of layersmay be equal to the number of antenna port(s) used for transmission ofthe physical channel.

The precoder may receive a block of vectors from the layer mapping andgenerate a block of vectors to be mapped onto resources on the antennaport(s). Precoding for spatial multiplexing using antenna port(s) withcell-specific reference signals may be used in combination with layermapping for spatial multiplexing. Spatial multiplexing may support twoor four antenna ports and the set of antenna ports used may be {0,1} or{0, 1, 2, 3}. Precoding for transmit diversity may be used incombination with layer mapping for transmit diversity. The precodingoperation for transmit diversity may be defined for two and four antennaports. Precoding for spatial multiplexing using antenna ports withUE-specific reference signals may also, for example, be used incombination with layer mapping for spatial multiplexing. Spatialmultiplexing using antenna ports with UE-specific reference signals maysupport up to eight antenna ports. Reference signals may be pre-definedsignals that may be used by the receiver for decoding the receivedphysical signal, estimating the channel state, and/or other purposes.

For antenna port(s) used for transmission of the physical channel, theblock of complex-valued symbols may be mapped in sequence to resourceelements. In resource blocks in which UE-specific reference signals arenot transmitted the PDSCH may be transmitted on the same set of antennaports as the physical broadcast channel in the downlink (PBCH). Inresource blocks in which UE-specific reference signals are transmitted,the PDSCH may be transmitted, for example, on antenna port(s) {5, {7},{8}, or {7, 8, . . . , v+6}, where v is the number of layers used fortransmission of the PDSCH.

Common reference signal(s) may be transmitted in physical antennaport(s). Common reference signal(s) may be cell-specific referencesignal(s) (RS) used for demodulation and/or measurement purposes.Channel estimation accuracy using common reference signal(s) may bereasonable for demodulation (high RS density). Common referencesignal(s) may be defined for LTE technologies, LTE-advancedtechnologies, and/or the like. Demodulation reference signal(s) may betransmitted in virtual antenna port(s) (i.e., layer or stream). Channelestimation accuracy using demodulation reference signal(s) may bereasonable within allocated time/frequency resources. Demodulationreference signal(s) may be defined for LTE-advanced technology and maynot be applicable to LTE technology. Measurement reference signal(s),may also called CSI (channel state information) reference signal(s), maybe transmitted in physical antenna port(s) or virtualized antennaport(s). Measurement reference signal(s) may be Cell-specific RS usedfor measurement purposes. Channel estimation accuracy may be relativelylower than demodulation RS. CSI reference signal(s) may be defined forLTE-advanced technology and may not be applicable to LTE technology.

In at least one of the various embodiments, uplink physical channel(s)may correspond to a set of resource elements carrying informationoriginating from higher layers. The following example uplink physicalchannel(s) may be defined for uplink: a) Physical Uplink Shared Channel(PUSCH), b) Physical Uplink Control Channel (PUCCH), c) Physical RandomAccess Channel (PRACH), and/or the like. Uplink physical signal(s) maybe used by the physical layer and may not carry information originatingfrom higher layers. For example, reference signal(s) may be consideredas uplink physical signal(s). Transmitted signal(s) in slot(s) may bedescribed by one or several resource grids including, for example,subcarriers and SC-FDMA or OFDMA symbols. Antenna port(s) may be definedsuch that the channel over which symbol(s) on antenna port(s) may beconveyed and/or inferred from the channel over which other symbol(s) onthe same antenna port(s) is/are conveyed. There may be one resource gridper antenna port. The antenna port(s) used for transmission of physicalchannel(s) or signal(s) may depend on the number of antenna port(s)configured for the physical channel(s) or signal(s).

Element(s) in a resource grid may be called a resource element. Aphysical resource block may be defined as N consecutive SC-FDMA symbolsin the time domain and/or M consecutive subcarriers in the frequencydomain, wherein M and N may be pre-defined integer values. Physicalresource block(s) in uplink(s) may comprise of M×N resource elements.For example, a physical resource block may correspond to one slot in thetime domain and 180 kHz in the frequency domain. Baseband signal(s)representing the physical uplink shared channel may be defined in termsof: a) scrambling, b) modulation of scrambled bits to generatecomplex-valued symbols, c) mapping of complex-valued modulation symbolsonto one or several transmission layers, d) transform precoding togenerate complex-valued symbols, e) precoding of complex-valued symbols,f) mapping of precoded complex-valued symbols to resource elements, g)generation of complex-valued time-domain SC-FDMA signal(s) for antennaport(s), and/or the like.

For codeword(s), block(s) of bits may be scrambled with UE-specificscrambling sequence(s) prior to modulation, resulting in block(s) ofscrambled bits. Complex-valued modulation symbols for codeword(s) to betransmitted may be mapped onto one, two, or more layers. For spatialmultiplexing, layer mapping(s) may be performed according to pre-definedformula (s). The number of layers may be less than or equal to thenumber of antenna port(s) used for transmission of physical uplinkshared channel(s). The example of a single codeword mapped to multiplelayers may be applicable when the number of antenna port(s) used forPUSCH is, for example, four. For layer(s), the block of complex-valuedsymbols may be divided into multiple sets, each corresponding to oneSC-FDMA symbol. Transform precoding may be applied. For antenna port(s)used for transmission of the PUSCH in a subframe, block(s) ofcomplex-valued symbols may be multiplied with an amplitude scalingfactor in order to conform to a required transmit power, and mapped insequence to physical resource block(s) on antenna port(s) and assignedfor transmission of PUSCH.

According to some of the various embodiments, data may arrive to thecoding unit in the form of two transport blocks every transmission timeinterval (TTI) per UL cell. The following coding actions may beidentified for transport block(s) of an uplink carrier: a) Add CRC tothe transport block, b) Code block segmentation and code block CRCattachment, c) Channel coding of data and control information, d) Ratematching, e) Code block concatenation. f) Multiplexing of data andcontrol information, g) Channel interleaver, h) Error detection may beprovided on UL-SCH (uplink shared channel) transport block(s) through aCyclic Redundancy Check (CRC), and/or the like. Transport block(s) maybe used to calculate CRC parity bits. Code block(s) may be delivered tochannel coding block(s). Code block(s) may be individually turboencoded. Turbo coded block(s) may be delivered to rate matchingblock(s).

Physical uplink control channel(s) (PUCCH) may carry uplink controlinformation. Simultaneous transmission of PUCCH and PUSCH from the sameUE may be supported if enabled by higher layers. For a type 2 framestructure, the PUCCH may not be transmitted in the UpPTS field. PUCCHmay use one resource block in each of the two slots in a subframe.Resources allocated to UE and PUCCH configuration(s) may be transmittedvia control messages. PUCCH may comprise: a) positive and negativeacknowledgements for data packets transmitted at least one downlinkcarrier, b) channel state information for at least one downlink carrier,c) scheduling request, and/or the like.

According to some of the various aspects of embodiments, cell search maybe the procedure by which a wireless device may acquire time andfrequency synchronization with a cell and may detect the physical layerCell ID of that cell (transmitter). An example embodiment forsynchronization signal and cell search is presented below. A cell searchmay support a scalable overall transmission bandwidth corresponding to 6resource blocks and upwards. Primary and secondary synchronizationsignals may be transmitted in the downlink and may facilitate cellsearch. For example, 504 unique physical-layer cell identities may bedefined using synchronization signals. The physical-layer cellidentities may be grouped into 168 unique physical-layer cell-identitygroups, group(s) containing three unique identities. The grouping may besuch that physical-layer cell identit(ies) is part of a physical-layercell-identity group. A physical-layer cell identity may be defined by anumber in the range of 0 to 167, representing the physical-layercell-identity group, and a number in the range of 0 to 2, representingthe physical-layer identity within the physical-layer cell-identitygroup. The synchronization signal may include a primary synchronizationsignal and a secondary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a primary synchronization signal may be generated from afrequency-domain Zadoff-Chu sequence according to a pre-defined formula.A Zadoff-Chu root sequence index may also be predefined in aspecification. The mapping of the sequence to resource elements maydepend on a frame structure. The wireless device may not assume that theprimary synchronization signal is transmitted on the same antenna portas any of the downlink reference signals. The wireless device may notassume that any transmission instance of the primary synchronizationsignal is transmitted on the same antenna port, or ports, used for anyother transmission instance of the primary synchronization signal. Thesequence may be mapped to the resource elements according to apredefined formula.

For FDD frame structure, a primary synchronization signal may be mappedto the last OFDM symbol in slots 0 and 10. For TDD frame structure, theprimary synchronization signal may be mapped to the third OFDM symbol insubframes 1 and 6. Some of the resource elements allocated to primary orsecondary synchronization signals may be reserved and not used fortransmission of the primary synchronization signal.

According to some of the various aspects of embodiments, the sequenceused for a secondary synchronization signal may be an interleavedconcatenation of two length-31 binary sequences. The concatenatedsequence may be scrambled with a scrambling sequence given by a primarysynchronization signal. The combination of two length-31 sequencesdefining the secondary synchronization signal may differ betweensubframe 0 and subframe 5 according to predefined formula (s). Themapping of the sequence to resource elements may depend on the framestructure. In a subframe for FDD frame structure and in a half-frame forTDD frame structure, the same antenna port as for the primarysynchronization signal may be used for the secondary synchronizationsignal. The sequence may be mapped to resource elements according to apredefined formula.

Example embodiments for the physical channels configuration will now bepresented. Other examples may also be possible. A physical broadcastchannel may be scrambled with a cell-specific sequence prior tomodulation, resulting in a block of scrambled bits. PBCH may bemodulated using QPSK, and/or the like. The block of complex-valuedsymbols for antenna port(s) may be transmitted during consecutive radioframes, for example, four consecutive radio frames. In some embodimentsthe PBCH data may arrive to the coding unit in the form of a onetransport block every transmission time interval (TTI) of 40 ms. Thefollowing coding actions may be identified. Add CRC to the transportblock, channel coding, and rate matching. Error detection may beprovided on PBCH transport blocks through a Cyclic Redundancy Check(CRC). The transport block may be used to calculate the CRC parity bits.The parity bits may be computed and attached to the BCH (broadcastchannel) transport block. After the attachment, the CRC bits may bescrambled according to the transmitter transmit antenna configuration.Information bits may be delivered to the channel coding block and theymay be tail biting convolutionally encoded. A tail bitingconvolutionally coded block may be delivered to the rate matching block.The coded block may be rate matched before transmission.

A master information block may be transmitted in PBCH and may includesystem information transmitted on broadcast channel(s). The masterinformation block may include downlink bandwidth, system framenumber(s), and PHICH (physical hybrid-ARQ indicator channel)configuration. Downlink bandwidth may be the transmission bandwidthconfiguration, in terms of resource blocks in a downlink, for example 6may correspond to 6 resource blocks, 15 may correspond to 15 resourceblocks and so on. System frame number(s) may define the N (for exampleN=8) most significant bits of the system frame number. The M (forexample M=2) least significant bits of the SFN may be acquiredimplicitly in the PBCH decoding. For example, timing of a 40 ms PBCH TTImay indicate 2 least significant bits (within 40 ms PBCH TTI, the firstradio frame: 00, the second radio frame: 01, the third radio frame: 10,the last radio frame: 11). One value may apply for other carriers in thesame sector of a base station (the associated functionality is common(e.g. not performed independently for each cell). PHICH configuration(s)may include PHICH duration, which may be normal (e.g. one symbolduration) or extended (e.g. 3 symbol duration).

Physical control format indicator channel(s) (PCFICH) may carryinformation about the number of OFDM symbols used for transmission ofPDCCHs (physical downlink control channel) in a subframe. The set ofOFDM symbols possible to use for PDCCH in a subframe may depend on manyparameters including, for example, downlink carrier bandwidth, in termsof downlink resource blocks. PCFICH transmitted in one subframe may bescrambled with cell-specific sequence(s) prior to modulation, resultingin a block of scrambled bits. A scrambling sequence generator(s) may beinitialized at the start of subframe(s). Block (s) of scrambled bits maybe modulated using QPSK. Block(s) of modulation symbols may be mapped toat least one layer and precoded resulting in a block of vectorsrepresenting the signal for at least one antenna port. Instances ofPCFICH control channel(s) may indicate one of several (e.g. 3) possiblevalues after being decoded. The range of possible values of instance(s)of the first control channel may depend on the first carrier bandwidth.

According to some of the various embodiments, physical downlink controlchannel(s) may carry scheduling assignments and other controlinformation. The number of resource-elements not assigned to PCFICH orPHICH may be assigned to PDCCH. PDCCH may support multiple formats.Multiple PDCCH packets may be transmitted in a subframe. PDCCH may becoded by tail biting convolutionally encoder before transmission. PDCCHbits may be scrambled with a cell-specific sequence prior to modulation,resulting in block(s) of scrambled bits. Scrambling sequencegenerator(s) may be initialized at the start of subframe(s). Block(s) ofscrambled bits may be modulated using QPSK. Block(s) of modulationsymbols may be mapped to at least one layer and precoded resulting in ablock of vectors representing the signal for at least one antenna port.PDCCH may be transmitted on the same set of antenna ports as the PBCH,wherein PBCH is a physical broadcast channel broadcasting at least onebasic system information field.

According to some of the various embodiments, scheduling controlpacket(s) may be transmitted for packet(s) or group(s) of packetstransmitted in downlink shared channel(s). Scheduling control packet(s)may include information about subcarriers used for packettransmission(s). PDCCH may also provide power control commands foruplink channels. OFDM subcarriers that are allocated for transmission ofPDCCH may occupy the bandwidth of downlink carrier(s). PDCCH channel(s)may carry a plurality of downlink control packets in subframe(s). PDCCHmay be transmitted on downlink carrier(s) starting from the first OFDMsymbol of subframe(s), and may occupy up to multiple symbol duration(s)(e.g. 3 or 4).

According to some of the various embodiments, PHICH may carry thehybrid-ARQ (automatic repeat request) ACK/NACK. Multiple PHICHs mappedto the same set of resource elements may constitute a PHICH group, wherePHICHs within the same PHICH group may be separated through differentorthogonal sequences. PHICH resource(s) may be identified by the indexpair (group, sequence), where group(s) may be the PHICH group number(s)and sequence(s) may be the orthogonal sequence index within thegroup(s). For frame structure type 1, the number of PHICH groups maydepend on parameters from higher layers (RRC). For frame structure type2, the number of PHICH groups may vary between downlink subframesaccording to a pre-defined arrangement. Block(s) of bits transmitted onone PHICH in one subframe may be modulated using BPSK or QPSK, resultingin a block(s) of complex-valued modulation symbols. Block(s) ofmodulation symbols may be symbol-wise multiplied with an orthogonalsequence and scrambled, resulting in a sequence of modulation symbols

Other arrangements for PCFICH, PHICH, PDCCH, and/or PDSCH may besupported. The configurations presented here are for example purposes.In another example, resources PCFICH, PHICH, and/or PDCCH radioresources may be transmitted in radio resources including a subset ofsubcarriers and pre-defined time duration in each or some of thesubframes. In an example, PUSCH resource(s) may start from the firstsymbol. In another example embodiment, radio resource configuration(s)for PUSCH, PUCCH, and/or PRACH (physical random access channel) may usea different configuration. For example, channels may be timemultiplexed, or time/frequency multiplexed when mapped to uplink radioresources.

According to some of the various aspects of embodiments, the physicallayer random access preamble may comprise a cyclic prefix of length Tcpand a sequence part of length Tseq. The parameter values may bepre-defined and depend on the frame structure and a random accessconfiguration. In an example embodiment, Tcp may be 0.1 msec, and Tseqmay be 0.9 msec. Higher layers may control the preamble format. Thetransmission of a random access preamble, if triggered by the MAC layer,may be restricted to certain time and frequency resources. The start ofa random access preamble may be aligned with the start of thecorresponding uplink subframe at a wireless device.

According to an example embodiment, random access preambles may begenerated from Zadoff-Chu sequences with a zero correlation zone,generated from one or several root Zadoff-Chu sequences. In anotherexample embodiment, the preambles may also be generated using otherrandom sequences such as Gold sequences. The network may configure theset of preamble sequences a wireless device may be allowed to use.According to some of the various aspects of embodiments, there may be amultitude of preambles (e.g. 64) available in cell(s). From the physicallayer perspective, the physical layer random access procedure mayinclude the transmission of random access preamble(s) and random accessresponse(s). Remaining message(s) may be scheduled for transmission by ahigher layer on the shared data channel and may not be considered partof the physical layer random access procedure. For example, a randomaccess channel may occupy 6 resource blocks in a subframe or set ofconsecutive subframes reserved for random access preamble transmissions.

According to some of the various embodiments, the following actions maybe followed for a physical random access procedure: 1) layer 1 proceduremay be triggered upon request of a preamble transmission by higherlayers; 2) a preamble index, a target preamble received power, acorresponding RA-RNTI (random access-radio network temporary identifier)and/or a PRACH resource may be indicated by higher layers as part of arequest; 3) a preamble transmission power P_PRACH may be determined; 4)a preamble sequence may be selected from the preamble sequence set usingthe preamble index; 5) a single preamble may be transmitted usingselected preamble sequence(s) with transmission power P_PRACH on theindicated PRACH resource; 6) detection of a PDCCH with the indicated RARmay be attempted during a window controlled by higher layers; and/or thelike. If detected, the corresponding downlink shared channel transportblock may be passed to higher layers. The higher layers may parsetransport block(s) and/or indicate an uplink grant to the physicallayer(s).

According to some of the various aspects of embodiments, a random accessprocedure may be initiated by a physical downlink control channel(PDCCH) order and/or by the MAC sublayer in a wireless device. If awireless device receives a PDCCH transmission consistent with a PDCCHorder masked with its radio identifier, the wireless device may initiatea random access procedure. Preamble transmission(s) on physical randomaccess channel(s) (PRACH) may be supported on a first uplink carrier andreception of a PDCCH order may be supported on a first downlink carrier.

Before a wireless device initiates transmission of a random accesspreamble, it may access one or many of the following types ofinformation: a) available set(s) of PRACH resources for the transmissionof a random access preamble; b) group(s) of random access preambles andset(s) of available random access preambles in group(s); c) randomaccess response window size(s); d) power-ramping factor(s); e) maximumnumber(s) of preamble transmission(s); f) initial preamble power; g)preamble format based offset(s); h) contention resolution timer(s);and/or the like. These parameters may be updated from upper layers ormay be received from the base station before random access procedure(s)may be initiated.

According to some of the various aspects of embodiments, a wirelessdevice may select a random access preamble using available information.The preamble may be signaled by a base station or the preamble may berandomly selected by the wireless device. The wireless device maydetermine the next available subframe containing PRACH permitted byrestrictions given by the base station and the physical layer timingrequirements for TDD or FDD. Subframe timing and the timing oftransmitting the random access preamble may be determined based, atleast in part, on synchronization signals received from the base stationand/or the information received from the base station. The wirelessdevice may proceed to the transmission of the random access preamblewhen it has determined the timing. The random access preamble may betransmitted on a second plurality of subcarriers on the first uplinkcarrier.

According to some of the various aspects of embodiments, once a randomaccess preamble is transmitted, a wireless device may monitor the PDCCHof a first downlink carrier for random access response(s), in a randomaccess response window. There may be a pre-known identifier in PDCCHthat identifies a random access response. The wireless device may stopmonitoring for random access response(s) after successful reception of arandom access response containing random access preamble identifiersthat matches the transmitted random access preamble and/or a randomaccess response address to a wireless device identifier. A base stationrandom access response may include a time alignment command. Thewireless device may process the received time alignment command and mayadjust its uplink transmission timing according the time alignment valuein the command. For example, in a random access response, a timealignment command may be coded using 11 bits, where an amount of thetime alignment may be based on the value in the command. In an exampleembodiment, when an uplink transmission is required, the base stationmay provide the wireless device a grant for uplink transmission.

If no random access response is received within the random accessresponse window, and/or if none of the received random access responsescontains a random access preamble identifier corresponding to thetransmitted random access preamble, the random access response receptionmay be considered unsuccessful and the wireless device may, based on thebackoff parameter in the wireless device, select a random backoff timeand delay the subsequent random access transmission by the backoff time,and may retransmit another random access preamble.

According to some of the various aspects of embodiments, a wirelessdevice may transmit packets on an uplink carrier. Uplink packettransmission timing may be calculated in the wireless device using thetiming of synchronization signal(s) received in a downlink. Uponreception of a timing alignment command by the wireless device, thewireless device may adjust its uplink transmission timing. The timingalignment command may indicate the change of the uplink timing relativeto the current uplink timing. The uplink transmission timing for anuplink carrier may be determined using time alignment commands and/ordownlink reference signals.

According to some of the various aspects of embodiments, a timealignment command may indicate timing adjustment for transmission ofsignals on uplink carriers. For example, a time alignment command mayuse 6 bits. Adjustment of the uplink timing by a positive or a negativeamount indicates advancing or delaying the uplink transmission timing bya given amount respectively.

For a timing alignment command received on subframe n, the correspondingadjustment of the timing may be applied with some delay, for example, itmay be applied from the beginning of subframe n+6. When the wirelessdevice's uplink transmissions in subframe n and subframe n+1 areoverlapped due to the timing adjustment, the wireless device maytransmit complete subframe n and may not transmit the overlapped part ofsubframe n+1.

According to some of the various aspects of embodiments, a wirelessdevice may include a configurable timer (timeAlignmentTimer) that may beused to control how long the wireless device is considered uplink timealigned. When a timing alignment command MAC control element isreceived, the wireless device may apply the timing alignment command andstart or restart timeAlignmentTimer. The wireless device may not performany uplink transmission except the random access preamble transmissionwhen timeAlignmentTimer is not running or when it exceeds its limit. Thetime alignment command may substantially align frame and subframereception timing of a first uplink carrier and at least one additionaluplink carrier. According to some of the various aspects of embodiments,the time alignment command value range employed during a random accessprocess may be substantially larger than the time alignment commandvalue range during active data transmission. In an example embodiment,uplink transmission timing may be maintained on a per time alignmentgroup (TAG) basis. Carrier(s) may be grouped in TAGs, and TAG(s) mayhave their own downlink timing reference, time alignment timer, and/ortime alignment commands. Group(s) may have their own random accessprocess. Time alignment commands may be directed to a time alignmentgroup. The TAG, including the primary cell may be called a primary TAG(pTAG) and the TAG not including the primary cell may be called asecondary TAG (sTAG).

According to some of the various aspects of embodiments, controlmessage(s) or control packet(s) may be scheduled for transmission in aphysical downlink shared channel (PDSCH) and/or physical uplink sharedchannel PUSCH. PDSCH and PUSCH may carry control and datamessage(s)/packet(s). Control message(s) and/or packet(s) may beprocessed before transmission. For example, the control message(s)and/or packet(s) may be fragmented or multiplexed before transmission. Acontrol message in an upper layer may be processed as a data packet inthe MAC or physical layer. For example, system information block(s) aswell as data traffic may be scheduled for transmission in PDSCH. Datapacket(s) may be encrypted packets.

According to some of the various aspects of embodiments, data packet(s)may be encrypted before transmission to secure packet(s) from unwantedreceiver(s). Desired recipient(s) may be able to decrypt the packet(s).A first plurality of data packet(s) and/or a second plurality of datapacket(s) may be encrypted using an encryption key and at least oneparameter that may change substantially rapidly over time. Theencryption mechanism may provide a transmission that may not be easilyeavesdropped by unwanted receivers. The encryption mechanism may includeadditional parameter(s) in an encryption module that changessubstantially rapidly in time to enhance the security mechanism. Examplevarying parameter(s) may comprise various types of system counter(s),such as system frame number. Substantially rapidly may for example implychanging on a per subframe, frame, or group of subframes basis.Encryption may be provided by a PDCP layer between the transmitter andreceiver, and/or may be provided by the application layer. Additionaloverhead added to packet(s) by lower layers such as RLC, MAC, and/orPhysical layer may not be encrypted before transmission. In thereceiver, the plurality of encrypted data packet(s) may be decryptedusing a first decryption key and at least one first parameter. Theplurality of data packet(s) may be decrypted using an additionalparameter that changes substantially rapidly over time.

According to some of the various aspects of embodiments, a wirelessdevice may be preconfigured with one or more carriers. When the wirelessdevice is configured with more than one carrier, the base station and/orwireless device may activate and/or deactivate the configured carriers.One of the carriers (the primary carrier) may always be activated. Othercarriers may be deactivated by default and/or may be activated by a basestation when needed. A base station may activate and deactivate carriersby sending an activation/deactivation MAC control element. Furthermore,the UE may maintain a carrier deactivation timer per configured carrierand deactivate the associated carrier upon its expiry. The same initialtimer value may apply to instance(s) of the carrier deactivation timer.The initial value of the timer may be configured by a network. Theconfigured carriers (unless the primary carrier) may be initiallydeactivated upon addition and after a handover.

According to some of the various aspects of embodiments, if a wirelessdevice receives an activation/deactivation MAC control elementactivating the carrier, the wireless device may activate the carrier,and/or may apply normal carrier operation including: sounding referencesignal transmissions on the carrier, CQI (channel qualityindicator)/PMI(precoding matrix indicator)/RI(ranking indicator)reporting for the carrier, PDCCH monitoring on the carrier, PDCCHmonitoring for the carrier, start or restart the carrier deactivationtimer associated with the carrier, and/or the like. If the devicereceives an activation/deactivation MAC control element deactivating thecarrier, and/or if the carrier deactivation timer associated with theactivated carrier expires, the base station or device may deactivate thecarrier, and may stop the carrier deactivation timer associated with thecarrier, and/or may flush HARQ buffers associated with the carrier.

If PDCCH on a carrier scheduling the activated carrier indicates anuplink grant or a downlink assignment for the activated carrier, thedevice may restart the carrier deactivation timer associated with thecarrier. When a carrier is deactivated, the wireless device may nottransmit SRS (sounding reference signal) for the carrier, may not reportCQI/PMI/RI for the carrier, may not transmit on UL-SCH for the carrier,may not monitor the PDCCH on the carrier, and/or may not monitor thePDCCH for the carrier.

A process to assign subcarriers to data packets may be executed by a MAClayer scheduler. The decision on assigning subcarriers to a packet maybe made based on data packet size, resources required for transmissionof data packets (number of radio resource blocks), modulation and codingassigned to data packet(s), QoS required by the data packets (i.e. QoSparameters assigned to data packet bearer), the service class of asubscriber receiving the data packet, or subscriber device capability, acombination of the above, and/or the like.

According to some of the various aspects of embodiments, packets may bereferred to service data units and/or protocols data units at Layer 1,Layer 2 and/or Layer 3 of the communications network. Layer 2 in an LTEnetwork may include three sub-layers: PDCP sub-layer, RLC sub-layer, andMAC sub-layer. A layer 2 packet may be a PDCP packet, an RLC packet or aMAC layer packet. Layer 3 in an LTE network may be Internet Protocol(IP) layer, and a layer 3 packet may be an IP data packet. Packets maybe transmitted and received via an air interface physical layer. Apacket at the physical layer may be called a transport block. Many ofthe various embodiments may be implemented at one or many differentcommunication network layers. For example, some of the actions may beexecuted by the PDCP layer and some others by the MAC layer.

According to some of the various aspects of embodiments, subcarriersand/or resource blocks may comprise a plurality of physical subcarriersand/or resource blocks. In another example embodiment, subcarriers maybe a plurality of virtual and/or logical subcarriers and/or resourceblocks.

According to some of the various aspects of embodiments, a radio bearermay be a GBR (guaranteed bit rate) bearer and/or a non-GBR bearer. A GBRand/or guaranteed bit rate bearer may be employed for transfer ofreal-time packets, and/or a non-GBR bearer may be used for transfer ofnon-real-time packets. The non-GBR bearer may be assigned a plurality ofattributes including: a scheduling priority, an allocation and retentionpriority, a portable device aggregate maximum bit rate, and/or the like.These parameters may be used by the scheduler in scheduling non-GBRpackets. GBR bearers may be assigned attributes such as delay, jitter,packet loss parameters, and/or the like.

According to some of the various aspects of embodiments, subcarriers mayinclude data subcarrier symbols and pilot subcarrier symbols. Pilotsymbols may not carry user data, and may be included in the transmissionto help the receiver to perform synchronization, channel estimationand/or signal quality detection. Base stations and wireless devices(wireless receiver) may use different methods to generate and transmitpilot symbols along with information symbols.

According to some of the various aspects of embodiments, the transmitterin the disclosed embodiments of the present invention may be a wirelessdevice (also called user equipment), a base station (also calledeNodeB), a relay node transmitter, and/or the like. The receiver in thedisclosed embodiments of the present invention may be a wireless device(also called user equipment-UE), a base station (also called eNodeB), arelay node receiver, and/or the like. According to some of the variousaspects of embodiments of the present invention, layer 1 (physicallayer) may be based on OFDMA or SC-FDMA. Time may be divided intoframe(s) with fixed duration. Frame(s) may be divided into substantiallyequally sized subframes, and subframe(s) may be divided intosubstantially equally sized slot(s). A plurality of OFDM or SC-FDMAsymbol(s) may be transmitted in slot(s). OFDMA or SC-FDMA symbol(s) maybe grouped into resource block(s). A scheduler may assign resource(s) inresource block unit(s), and/or a group of resource block unit(s).Physical resource block(s) may be resources in the physical layer, andlogical resource block(s) may be resource block(s) used by the MAClayer. Similar to virtual and physical subcarriers, resource block(s)may be mapped from logical to physical resource block(s). Logicalresource block(s) may be contiguous, but corresponding physical resourceblock(s) may be non-contiguous. Some of the various embodiments of thepresent invention may be implemented at the physical or logical resourceblock level(s).

According to some of the various aspects of embodiments, layer 2transmission may include PDCP (packet data convergence protocol), RLC(radio link control), MAC (media access control) sub-layers, and/or thelike. MAC may be responsible for the multiplexing and mapping of logicalchannels to transport channels and vice versa. A MAC layer may performchannel mapping, scheduling, random access channel procedures, uplinktiming maintenance, and/or the like.

According to some of the various aspects of embodiments, the MAC layermay map logical channel(s) carrying RLC PDUs (packet data unit) totransport channel(s). For transmission, multiple SDUs (service dataunit) from logical channel(s) may be mapped to the Transport Block (TB)to be sent over transport channel(s). For reception, TBs from transportchannel(s) may be demultiplexed and assigned to corresponding logicalchannel(s). The MAC layer may perform scheduling related function(s) inboth the uplink and downlink and thus may be responsible for transportformat selection associated with transport channel(s). This may includeHARQ functionality. Since scheduling may be done at the base station,the MAC layer may be responsible for reporting scheduling relatedinformation such as UE (user equipment or wireless device) bufferoccupancy and power headroom. It may also handle prioritization fromboth an inter-UE and intra-UE logical channel perspective. MAC may alsobe responsible for random access procedure(s) for the uplink that may beperformed following either a contention and non-contention basedprocess. UE may need to maintain timing synchronization with cell(s).The MAC layer may perform procedure(s) for periodic synchronization.

According to some of the various aspects of embodiments, the MAC layermay be responsible for the mapping of multiple logical channel(s) totransport channel(s) during transmission(s), and demultiplexing andmapping of transport channel data to logical channel(s) duringreception. A MAC PDU may include of a header that describes the formatof the PDU itself, which may include control element(s), SDUs, Padding,and/or the like. The header may be composed of multiple sub-headers, onefor constituent part(s) of the MAC PDU. The MAC may also operate in atransparent mode, where no header may be pre-pended to the PDU.Activation command(s) may be inserted into packet(s) using a MAC controlelement.

According to some of the various aspects of embodiments, the MAC layerin some wireless device(s) may report buffer size(s) of either a singleLogical Channel Group (LCG) or a group of LCGs to a base station. An LCGmay be a group of logical channels identified by an LCG ID. The mappingof logical channel(s) to LCG may be set up during radio configuration.Buffer status report(s) may be used by a MAC scheduler to assign radioresources for packet transmission from wireless device(s). HARQ and ARQprocesses may be used for packet retransmission to enhance thereliability of radio transmission and reduce the overall probability ofpacket loss.

According to some of the various aspects of embodiments, an RLCsub-layer may control the applicability and functionality of errorcorrection, concatenation, segmentation, re-segmentation, duplicatedetection, in-sequence delivery, and/or the like. Other functions of RLCmay include protocol error detection and recovery, and/or SDU discard.The RLC sub-layer may receive data from upper layer radio bearer(s)(signaling and data) called service data unit(s) (SDU). The transmissionentities in the RLC layer may convert RLC SDUs to RLC PDU afterperforming functions such as segmentation, concatenation, adding RLCheader(s), and/or the like. In the other direction, receiving entitiesmay receive RLC PDUs from the MAC layer. After performing reordering,the PDUs may be assembled back into RLC SDUs and delivered to the upperlayer. RLC interaction with a MAC layer may include: a) data transferfor uplink and downlink through logical channel(s); b) MAC notifies RLCwhen a transmission opportunity becomes available, including the size oftotal number of RLC PDUs that may be transmitted in the currenttransmission opportunity, and/or c) the MAC entity at the transmittermay inform RLC at the transmitter of HARQ transmission failure.

According to some of the various aspects of embodiments, PDCP (packetdata convergence protocol) may comprise a layer 2 sub-layer on top ofRLC sub-layer. The PDCP may be responsible for a multitude of functions.First, the PDCP layer may transfer user plane and control plane data toand from upper layer(s). PDCP layer may receive SDUs from upper layer(s)and may send PDUs to the lower layer(s). In other direction, PDCP layermay receive PDUs from the lower layer(s) and may send SDUs to upperlayer(s). Second, the PDCP may be responsible for security functions. Itmay apply ciphering (encryption) for user and control plane bearers, ifconfigured. It may also perform integrity protection for control planebearer(s), if configured. Third, the PDCP may perform header compressionservice(s) to improve the efficiency of over the air transmission. Theheader compression may be based on robust header compression (ROHC).ROHC may be performed on VOIP packets. Fourth, the PDCP may beresponsible for in-order delivery of packet(s) and duplicate detectionservice(s) to upper layer(s) after handover(s). After handover, thesource base station may transfer unacknowledged packet(s)s to targetbase station when operating in RLC acknowledged mode (AM). The targetbase station may forward packet(s)s received from the source basestation to the UE (user equipment).

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example,” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLab VIEWMathScript. Additionally, it may be possible to implementmodules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. Finally, it needs to beemphasized that the above mentioned technologies are often used incombination to achieve the result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above described exampleembodiments. In particular, it should be noted that, for examplepurposes, the above explanation has focused on the example(s) using FDDcommunication systems. However, one skilled in the art will recognizethat embodiments of the invention may also be implemented in TDDcommunication systems. The disclosed methods and systems may beimplemented in wireless or wireline systems. The features of variousembodiments presented in this invention may be combined. One or manyfeatures (method or system) of one embodiment may be implemented inother embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112, paragraph 6. Claims that do not expressly include the phrase“means for” or “step for” are not to be interpreted under 35 U.S.C. 112,paragraph 6.

What is claimed is:
 1. A method comprising: transmitting, by a firstbase station, a first physical downlink control channel associated withone or more wireless devices in communication with the first basestation, wherein the first physical downlink control channel istransmitted in fewer than all subframes of a frame and begins in time ata first symbol number in a series of symbols of a subframe; andtransmitting, by a second base station, a second physical downlinkcontrol channel associated with one or more wireless devices incommunication with the second base station, wherein second radioresources of the second physical downlink control channel are configuredbased on the first symbol number of the first physical downlink controlchannel to manage overlap with first radio resources of the firstphysical downlink control channel.
 2. The method of claim 1, furthercomprising receiving, by the second base station and from the first basestation, a bitmap indicating the first radio resources of the firstphysical downlink control channel.
 3. The method of claim 1, wherein thefirst physical downlink control channel is a first enhanced physicaldownlink control channel (ePDCCH), and the method further comprisestransmitting first scheduling packets via the first ePDCCH, the firstscheduling packets comprising scheduling information for a firstphysical downlink data channel.
 4. The method of claim 1, wherein thesecond physical downlink control channel is a second enhanced physicaldownlink control channel (ePDCCH).
 5. The method of claim 4, furthercomprising transmitting, via the second ePDCCH, scheduling packets forthe one or more wireless devices in communication with the second basestation.
 6. The method of claim 1, further comprising transmitting, bythe first base station and to the second base station, at least onemessage indicating the first symbol number.
 7. The method of claim 1,wherein the second radio resources of the second physical downlinkcontrol channel that are configured based on the first symbol number tomanage overlap with the first radio resources of the first physicaldownlink control channel are configured based on the first symbol numberto reduce overlap or avoid overlap with the first radio resources of thefirst physical downlink control channel.
 8. A system comprising: a firstbase station comprising: one or more processors; and one or morememories storing instructions that, when executed by the one or moreprocessors of the first base station, cause the first base station totransmit a first physical downlink control channel associated with oneor more wireless devices in communication with the first base station,wherein the first physical downlink control channel is transmitted infewer than all subframes of a frame and begins in time at a first symbolnumber in a series of symbols of a subframe; and a second base stationcomprising: one or more processors; and one or more memories storinginstructions that, when executed by the one or more processors of thesecond base station, cause the second base station to transmit a secondphysical downlink control channel associated with one or more wirelessdevices in communication with the second base station, wherein secondradio resources of the second physical downlink control channel areconfigured based on the first symbol number of the first physicaldownlink control channel to manage overlap with first radio resources ofthe first physical downlink control channel.
 9. The system of claim 8,wherein the one or more memories of the second base station furtherstore instructions that, when executed by the one or more processors ofthe second base station, cause the second base station to receive, fromthe first base station, a bitmap indicating the first radio resources ofthe first physical downlink control channel.
 10. The system of claim 8,wherein the first physical downlink control channel is a first enhancedphysical downlink control channel (ePDCCH), and wherein the one or morememories of the first base station further store instructions that, whenexecuted by the one or more processors of the first base station, causethe first base station to transmit first scheduling packets via thefirst ePDCCH, the first scheduling packets comprising schedulinginformation for a first physical downlink data channel.
 11. The systemof claim 8, wherein the second physical downlink control channel is asecond enhanced physical downlink control channel (ePDCCH).
 12. Thesystem of claim 8, wherein the one or more memories of the first basestation further store instructions that, when executed by the one ormore processors of the first base station, cause the first base stationto transmit, to the second base station, at least one message indicatingthe first symbol number.
 13. The system of claim 8, wherein the one ormore memories of the second base station further store instructionsthat, when executed by the one or more processors of the second basestation, cause the second base station to manage the second radioresources of the second physical downlink control channel to reduceoverlap or avoid overlap with the first radio resources of the firstphysical downlink control channel.
 14. A method comprising: determining,by a second base station, a symbol number of a starting symbol in timeof first radio resources of a first physical downlink control channeltransmitted by a first base station; determining, by the second basestation and based on the symbol number of the starting symbol in time,second radio resources of a second physical downlink control channel ofthe second base station to manage overlap with the first radio resourcesof the first physical downlink control channel; and transmitting, by thesecond base station, the second physical downlink control channel usingthe determined second radio resources.
 15. The method of claim 14,wherein the first physical downlink control channel occurs in fewer thanall subframes of a frame.
 16. The method of claim 14, wherein the secondphysical downlink control channel is an enhanced physical downlinkcontrol channel (ePDCCH).
 17. The method of claim 14, wherein thedetermining the second radio resources of the second physical downlinkcontrol channel of the second base station to manage overlap with firstradio resources of the first physical downlink control channel furthercomprises at least one of reducing overlap or avoiding overlap betweenthe first radio resources of the first physical downlink control channelof the first base station and the second radio resources of the secondphysical downlink control channel of the second base station.
 18. Themethod of claim 14, wherein the determining the symbol number of thestarting symbol in time comprises receiving, by the second base stationand from the first base station, at least one message indicating thesymbol number of the starting symbol in time.
 19. The method of claim14, wherein the first physical downlink control channel occurs in fewerthan all subframes of a frame, and the method further comprisesreceiving, by the second base station and from the first base station, abitmap indicating the first radio resources of the first physicaldownlink control channel.
 20. A second base station comprising: one ormore processors; and one or more memories storing one or moreinstructions that, when executed by the one or more processors, causethe second base station to perform the following: determine a symbolnumber of a starting symbol in time of first radio resources of a firstphysical downlink control channel transmitted by a first base station;determine, based on the symbol number of the starting symbol in time,second radio resources of a second physical downlink control channel ofthe second base station to manage overlap with the first radio resourcesof the first physical downlink control channel; and transmit the secondphysical downlink control channel using the determined second radioresources.
 21. The second base station of claim 20, wherein the firstradio resources of the first physical downlink control channel comprisefewer than all subframes of a frame.
 22. The second base station ofclaim 20, wherein the second physical downlink control channel is anenhanced physical downlink control channel (ePDCCH).
 23. The second basestation of claim 20, wherein the instructions that cause the second basestation to determine the second radio resources of the second physicaldownlink control channel of the second base station to manage overlapwith first radio resources of the first physical downlink controlchannel further cause the second base station to reduce overlap or avoidoverlap between the first radio resources of the first physical downlinkcontrol channel of the first base station and the second radio resourcesof the second physical downlink control channel of the second basestation.
 24. The second base station of claim 20, wherein theinstructions that cause the second base station to determine the symbolnumber of the starting symbol in time cause the second base station toreceive, from the first base station, at least one message indicatingthe symbol number of the starting symbol in time.
 25. The second basestation of claim 20, wherein the first physical downlink control channelcomprises fewer than all subframes of a frame, and the one or morememories further store instructions that, when executed by the one ormore processors, cause the second base station to receive, from thefirst base station, a bitmap indicating the first radio resources of thefirst physical downlink control channel.
 26. A method comprising:transmitting, by a first base station, a first physical downlink controlchannel associated with one or more wireless devices in communicationwith the first base station, wherein the first physical downlink controlchannel is transmitted in fewer than all subframes of a frame and istransmitted employing a first beamforming codeword; and transmitting, bya second base station, a second physical downlink control channelassociated with one or more wireless devices in communication with thesecond base station, wherein the second physical downlink controlchannel is transmitted in fewer than all subframes of a frame and istransmitted employing a second beamforming codeword, wherein at leastone of the first beamforming codeword or the second beamforming codewordis configured to manage inter-cell interference between the firstphysical downlink control channel and the second physical downlinkcontrol channel.
 27. The method of claim 26, wherein the at least one ofthe first beamforming codeword or the second beamforming codeword isconfigured to reduce inter-cell interference or avoid inter-cellinterference between the first physical downlink control channel and thesecond physical downlink control channel.
 28. The method of claim 26,wherein the first physical downlink control channel is a first enhancedphysical downlink control channel (ePDCCH), and the method furthercomprises transmitting first scheduling packets via the first ePDCCH,the first scheduling packets comprising scheduling information for afirst physical downlink data channel.
 29. The method of claim 26,wherein the second physical downlink control channel is a secondenhanced physical downlink control channel (ePDCCH).
 30. The method ofclaim 29, further comprising transmitting, via the second ePDCCH,scheduling packets for the one or more wireless devices in communicationwith the second base station.
 31. The method of claim 26, furthercomprising transmitting, by the first base station and to the secondbase station, at least one message indicating the first beamformingcodeword.
 32. A system comprising: a first base station comprising: oneor more processors; and one or more memories storing instructions that,when executed by the one or more processors of the first base station,cause the first base station to transmit a first physical downlinkcontrol channel associated with one or more wireless devices incommunication with the first base station, wherein the first physicaldownlink control channel is transmitted in fewer than all subframes of aframe and is transmitted employing a first beamforming codeword; and asecond base station comprising: one or more processors; and one or morememories storing instructions that, when executed by the one or moreprocessors of the second base station, cause the second base station totransmit a second physical downlink control channel associated with oneor more wireless devices in communication with the second base station,wherein the second physical downlink control channel is transmitted infewer than all subframes of a frame and is transmitted employing asecond beamforming codeword, wherein at least one of the firstbeamforming codeword or the second beamforming codeword is configured tomanage inter-cell interference between the first physical downlinkcontrol channel and the second physical downlink control channel. 33.The system of claim 32, wherein the at least one of the firstbeamforming codeword or the second beamforming codeword is configured toreduce inter-cell interference or avoid inter-cell interference betweenthe first physical downlink control channel and the second physicaldownlink control channel.
 34. The system of claim 32, wherein the firstphysical downlink control channel is a first enhanced physical downlinkcontrol channel (ePDCCH), and the one or more memories of the first basestation further store instructions that, when executed by the one ormore processors of the first base station, cause the first base stationto transmit first scheduling packets via the first ePDCCH, the firstscheduling packets comprising scheduling information for a firstphysical downlink data channel.
 35. The system of claim 32, wherein thesecond physical downlink control channel is a second enhanced physicaldownlink control channel (ePDCCH).
 36. The system of claim 35, whereinthe one or more memories of the second base station further storeinstructions that, when executed by the one or more processors of thesecond base station, cause the second base station to transmit, via thesecond ePDCCH, scheduling packets for the one or more wireless devicesin communication with the second base station.
 37. The system of claim32, wherein the one or more memories of the first base station furtherstore instructions that, when executed by the one or more processors ofthe first base station, cause the first base station to transmit, to thesecond base station, at least one message indicating the firstbeamforming codeword.